Meepo
[wiki] rating: 2.0 (winrate: 56% pickrate: 1%)Skywrath Mage
[wiki] rating: 2.0 (winrate: 50% pickrate: 10%)Storm Spirit
* Similar to 
Timbersaw, Storm Spirit builds items that don't help against silences.
* An 
Orchid Malevolence will most likely silence you first. However, if you grab a 
Eul's Scepter of Divinity, you might dispel his silence and turn the tides to your favor.
* Root and silence are 
Storm Spirit's ultimate counters. Skywrath Mage has a silence in his kit, and has 
Rod of Atos as his core item. If he dispels one, you cast the other, both leaving him vulnerable.
* If he builds 
Black King Bar, he spends 4050 gold that doesn't help him snowball effectively.
Legion Commander
* 
Mystic Flare can easily burst down Legion Commander while she is Dueling.
Treant Protector
[wiki] rating: 1.6 (winrate: 53% pickrate: 16%)Storm Spirit
* If Storm Spirit is caught in an Overgrowth, he is shut down.
* With the exception of 
Electric Vortex, he won't be able to cast any relevant skill.
Legion Commander
* Heroes with global abilities can give Legion Commander's opponent an edge in Duels from anywhere on the map: 
Nature's Prophet, 
Ancient Apparition, 
Zeus, 
Invoker, 
Treant Protector
Outworld Destroyer
[wiki] rating: 1.6 (winrate: 51% pickrate: 10%)Storm Spirit
* Heroes with mana burn: 
Nyx Assassin, Invoker, 
Outworld Destroyer, 
Pugna, 
Lion
Legion Commander
* 
Astral Imprisonment prevents Legion Commander from killing her opponents in Duels.
Additional:
* Outworld Destroyer can save an ally hero caught by 
Duel with Astral Imprisonment, and he can inflict heavy damage on Legion Commander with Arcane Orb to aid his ally. However, if he gets caught, he is unlikely to survive the duel, due to his lack of durability.
Tusk
[wiki] rating: 1.6 (winrate: 49% pickrate: 15%)Storm Spirit
* Tusks damage/stun is enough to obliviate Storm Spirit before he can do anything.
* Tusk is a common 
Blink Dagger carrier, and once he reaches Level 18, 
Walrus PUNCH! deals roughly half of Storm Spirit's health alone, It also stuns for a long enough time for Tusk to 
Snowball Storm Spirit, stunning him even more, If that hasn't finished him off, the damage from 
Ice Shards probably will. Combined with 
Tag Team, which adds bonus damage to Tusks attacks, Storm Spirit is unlikely to survive Tusk initiating on him
* Walrus PUNCH is even more potent if he uses a 
Silver Edge instead
* However while Ball Lightning doesn't disjoint Snowball, if used before Tusk hits with Snowball, prevents the stun and damage from being applied
Legion Commander
* Heroes who can hide the Dueled target (Outworld Destroyer, 
Shadow Demon, 
Tusk, 
Phoenix with 
Aghanim's Scepter etc).
Additional:
* Walrus PUNCH! makes Legion Commander lose Duel easily, especially when she doesn't have 
Blade Mail. Tusk can also snowball dueled allies, preventing them from taking damage for a large portion of the duel's duration.
Sven
[wiki] rating: 1.6 (winrate: 48% pickrate: 2%)Storm Spirit
* Heroes who cannot prevent Sven from killing towers will often struggle from a small map very early, such as 
Phantom Assassin, Storm Spirit and 
Phantom Lancer.
Legion Commander
* 
God's Strength makes Sven one of the worst heroes to Duel.
* 
Storm Hammer can be used to interrupt Duels.
* 
Warcry gives a big boost in passive defensive ability with the active component to nearby allies.
* With the Aghanim Shard Warcry also gives nearby allies passive increases.
Troll Warlord
[wiki] rating: 1.2 (winrate: 50% pickrate: 2%)Storm Spirit
* Mobility heroes will often be rooted by Troll Warlord and unable to escape, like Storm Spirit.
Legion Commander
* 
Troll Warlord's melee bash and high attack speed can often help him and his allies win Duels against Legion Commander.
Omniknight
[wiki] rating: 1.0 (winrate: 55% pickrate: 3%)Legion Commander
* 
Purification prevents Legion Commander from killing her target, and will always hit her during Duels.
* 
Guardian Angel completely wastes Duel's duration, and can save an ally across the map when upgraded with Aghanim's Scepter.
Additional:
* Both Guardian Angel and Purification are perfect counters against Duel.
Lone Druid
[wiki] rating: 1.0 (winrate: 55% pickrate: 3%)Storm Spirit
* True Form gives Lone Druid a huge amount of health that no amount of 
Ball Lightning will chip through.
* 
Entangling Claws can mean a very quick end to the Storm Spirit as it prevents him from using Ball Lightning all together.
* Storm Spirit is a single target nuker, with the Shard Lone Druid can always fear him away from himself or the bear, defending the target he does not go on. This is assuming he cannot try and proc his entangle or a potential 
Skull Basher.
Visage
[wiki] rating: 1.0 (winrate: 55% pickrate: 2%)Legion Commander
* 
Gravekeeper's Cloak protects Visage from Legion Commander's attacks for most of Duel's duration.
* Chain stuns from Visage's familiars prevents Legion Commander from winning Duels.
Dazzle
[wiki] rating: 1.0 (winrate: 52% pickrate: 9%)Legion Commander
* 
Shallow Grave prevents Legion Commander from killing her opponents in Duels.
* 
Shadow Wave will heal an ally caught in a Duel, as well as dealing damage to Legion Commander.
Night Stalker
[wiki] rating: 1.0 (winrate: 52% pickrate: 4%)Storm Spirit
* Storm Spirit is absolutely helpless if caught within Night Stalker's silence range.
* Common items a Storm Spirit will build will not remove the AoE silence.
Additional:
* 
Crippling Fear is a silence that can last up to 8 seconds during night, rendering Storm Spirit tied limited to his items in a fight.
* 
Dark Ascension allows Night Stalker to initiate on Storm Spirit across the impassable terrain around the middle lane, rendering Storm vulnerable in the early game and prevent him from snowballing.
Naga Siren
[wiki] rating: 1.0 (winrate: 51% pickrate: 3%)Storm Spirit
* 
Ensnare prevents using any kind of movement abiilties, Making Naga Siren good against heroes who rely on gap-closing abilities to escape: Phantom Assassin, 
Magnus, 
Slark, 
Riki, 
Faceless Void, Storm Spirit.
Legion Commander
* Song of the Siren lasts long enough to prevent a successful Duel (but only if Naga wasn't the target).
Legion Commander
* Heroes who rely on illusions will see them destroyed easily by Overwhelming Odds: Phantom Lancer, 
Chaos Knight, 
Terrorblade, 
Naga Siren
Underlord
[wiki] rating: 1.0 (winrate: 51% pickrate: 3%)Legion Commander
* 
Atrophy Aura's percentage-based damage reduction greatly diminishes Legion Commander's overall damage output, even if she has won many Duels
* Legion Commander cannot get out the way of Firestorm because she is stationary.
Additional:
* Atrophy Aura makes it hard for Legion Commander to win Duels.
* 
Fiend's Gate can be used to save Underlord and his allies from a Duel or to intercept Legion Commander, because outside from 
Overwhelming Odds, Legion Commander has no other area-of-effect abilities.
Abaddon
[wiki] rating: 1.0 (winrate: 50% pickrate: 6%)Legion Commander
* If he isn't broken (break), Abaddon can use Borrowed Time to waste Legion Commander's Duel, As Borrowed Time has a shorter cooldown, Legion Commander can't win duels, effectively reducing her targets by one, Duel also means that Borrowed Time heals Abaddon for the duration of the duel, as Legion can't stop attacking.
Additional:
* 
Aphotic Shield and 
Mist Coil makes it hard for Legion Commander to kill Abaddon's teammates in Duels.
* 
Borrowed Time makes Abaddon nearly impossible to kill in Duels, and often replenishes much of his health because Legion Commander cannot manually stop attacking during Duels.
Dawnbreaker
[wiki] rating: 1.0 (winrate: 50% pickrate: 8%)Legion Commander
* Solar Guardian can save allies who are being dueled and will interrupt her Duel initiation.
Slardar
[wiki] rating: 1.0 (winrate: 50% pickrate: 4%)Legion Commander
* With armor items like 
Solar Crest or 
Assault Cuirass combined with Bash of the Deep, Slardar can easily tank the Duel, If not dueled himself, he can drop 
Legion Commander's armor during duel and/or buff his teammate and save them, leaving her only the choice of dueling supports which can also be saved with fast Blink into Slithereen Crush.
Clockwerk
[wiki] rating: 1.0 (winrate: 49% pickrate: 8%)Legion Commander
* Battery Assault's mini-stuns can severely disrupt Legion Commander's attack animation when she enters a Duel, potentially saving Clockwerk (or his allies) and possibly even giving him an edge in securing a win himself.
* Power Cogs pushes Legion Commander away from Clockwerk's allies when she enters a Duel.
Axe
[wiki] rating: 1.0 (winrate: 49% pickrate: 9%)Legion Commander
* Axe usually wants to fight in the middle of creep waves to proc his 
Counter Helix. Legion Commander wants to do the same thing to proc Moment of Courage, often resulting in Axe getting a huge amount of damage in against Legion Commander.
* Axe's high armor gain thanks to 
Culling Blade makes him almost impossible to kill during a Duel in the late game.
Disruptor
[wiki] rating: 1.0 (winrate: 48% pickrate: 10%)Storm Spirit
* At around the 10-minute mark, Disruptor would normally be level 6 or 7. This means you can have a level 3/4 glimpse along with Static Storm. A high level glimpse is enough to pull Storm back to a Static Storm even after he used Ball Lightning due to his limited mana pool at that time.
* Be careful in the late game however, as there is a good chance he will kill you straight-out before Glimpse has finished bringing him back. Therefore Glimpse would simply bring him back to safety after he's murdered you or a teammate. Of course, this is assuming he hasn't silenced you with an item.
Winter Wyvern
[wiki] rating: 1.0 (winrate: 48% pickrate: 3%)Legion Commander
* 
Cold Embrace saves allies from dying in Duels.
* 
Winter's Curse turns Legion Commander's high damage against her allies, giving the enemy team little time to react.
* However, Winter Wyvern lanes very poorly against Legion Commander due to Press the Attack removing all the debuffs she can give. Winter Wyvern also has little chances of surviving if she gets Dueled herself.
Additional:
* Cold Embrace is very effective against Duel.
* Also, casting Winter's Curse at Legion Commander while an ally is in a Duel will stun her for most of the duration, possibly preventing lethal damage dealt to your ally. It can also turn her high-damage against her teammate.
Bane
[wiki] rating: 1.0 (winrate: 48% pickrate: 2%)Storm Spirit
* 
Wraith King, 
Medusa, Storm Spirit and other mana dependent heroes will have diminished impact on a fight if they survive Fiend's Grip due to its mana steal.
Legion Commander
* Bane has powerful single-target abilities that can help his allies win Duels, or at least cripple Legion Commander for the duration.
* Nightmare can waste Duel's entire duration as the dueled units transfer the Nightmare back and forth. This may be prevented if a non-Dueling unit attacks the Nightmared Dueler.
Additional:
* 
Enfeeble, 
Nightmare and 
Fiend's Grip all prevent Legion Commander from winning Duels, especially when Bane has Blink Dagger.
Legion Commander
* Heroes with strong dispels can dispel Bane's disables from their allies: 
Oracle, Legion Commander, 
Omniknight.
Witch Doctor
[wiki] rating: 1.0 (winrate: 48% pickrate: 15%)Legion Commander
* 
Paralyzing Cask can save ally from Legion Commander Duel's until she purchase Aghanim's Scepter.
* 
Voodoo Restoration can heal Witch Doctor allies from Duel's.
* 
Death Ward can help Witch Doctor allies from winning Duel's, if, he is not a target.
Faceless Void
[wiki] rating: 1.0 (winrate: 48% pickrate: 9%)Storm Spirit
* Time Dilation while 
Static Remnant and Electric Vortex are on cooldown will make these abilities unusable for a long time, reducing Storm Spirit's potential.
* Faceless Void can catch Storm Spirit during Ball Lightning with a well-timed Chronosphere or Time Walk.
Doom
[wiki] rating: 1.0 (winrate: 47% pickrate: 8%)Storm Spirit
* 
Doom prevents Storm Spirit from using all of his abilities and items, rendering Storm Spirit useless in a fight.
Medusa
[wiki] rating: 1.0 (winrate: 45% pickrate: 1%)Legion Commander
* 
Mana Shield makes Medusa very hard to take down in Duels.
* 
Stone Gaze stops Legion Commander from Dueling altogether, regardless of who she targets.
Riki
[wiki] rating: 0.6 (winrate: 54% pickrate: 13%)Storm Spirit
* Smoke Cloud prevents Storm Spirit from using any of his offensive and defensive spells, rendering him unable to effectively react to Riki's attack.
Additional:
* 
Smoke Screen prevents Storm Spirit from using his abilities once inside the radius. Riki can utilize this ability to allow his team to fight around Smoke Screen so that Storm Spirit cannot spam his spells to proc 
Overload.
Legion Commander
* Heroes with abilities that blind or cause Legion Commander to miss will prevent her from winning Duels: 
Arc Warden, 
Keeper of the Light, Riki, 
Tinker
Legion Commander
* Another great threat to Riki since her Duel forces him to fight from the front and expose him for the entire duration, almost always guaranteeing an easy win (unless Riki has allies helping him).
* 
Moment of Courage can become hard to deal with as it doesn't cease with silence.
Phoenix
[wiki] rating: 0.6 (winrate: 50% pickrate: 5%)Legion Commander
* Heroes who can hide the Dueled target (Outworld Destroyer, Shadow Demon, Tusk, Phoenix with Aghanim's Scepter etc).
Additional:
* Legion Commander relies on her powerful attack and her Duel to be effective. But if Phoenix gets the jump on her first, she can find herself severely slowed, taking heavy damage, and find herself unable to Duel a burning Supernova.
* It must be noted that 
Press the Attack will both dispel the attack slow of Fire Spirits and grant her or whoever she targets bonus attack speed. This allows her to easily destroy a Supernova if caution is not taken to prevent this from occurring. As such, it would be a better decision to simply avoid a farmed or skilled Legion Commander instead of attempting to overpower her.
* If an ally is caught by Duel, Phoenix can use Sun Ray to heal the ally and damage Legion Commander, possibly swinging the Duel in their team's favor. Or with Aghanim's Scepter, Phoenix can save an ally from dying in Duel with Supernova and cancel the Duel as well.
Necrophos
[wiki] rating: 0.6 (winrate: 50% pickrate: 7%)Storm Spirit
* Heroes that have escape abilities (such as 
Queen of Pain, Storm Spirit or Timbersaw) can be either nullified by Reaper's Scythe or a complimentary item for Necrophos (like Rod of Atos or 
Scythe of Vyse). If Necrophos is quick enough and enters range, they can quickly, if not instantly, die if they are not quick enough.
Shadow Shaman
[wiki] rating: 0.6 (winrate: 49% pickrate: 6%)Storm Spirit
* In general, squishy heroes that rely on escape often struggles against the amount of disables Shadow Shaman can bring. Queen of Pain, 
Anti-Mage and Storm Spirit are among these.
Legion Commander
* Heroes with long or multiple disables will prevent Legion Commander from winning Duels: 
Shadow Shaman, Lion
Legion Commander
* 
Pudge, Legion Commander and 
Axe will make the match a living hell for Shadow Shaman, since they are known for surprise attacks from the fog and quickly killing low HP heroes. They can also interrupt Shadow Shaman's channeling, Legion being especially problematic, as she can use Press the Attack on an ally who is hexed as well.
Puck
[wiki] rating: 0.6 (winrate: 48% pickrate: 9%)Storm Spirit
* Any Hero with high mobility will be neutralized by dream coil: Queen of Pain, Storm Spirit, 
Ember Spirit, 
Lycan, 
Bloodseeker, Anti-Mage, Timbersaw
Wraith King
[wiki] rating: 0.6 (winrate: 48% pickrate: 4%)Legion Commander
* Wraith King's 
Reincarnation allows him to severely punish Legion Commander after he revives, as her abilities are on cooldown. Legion Commander is still awarded a Duel win if Wraith King reincarnates.
Additional:
* Wraith King makes a poor Duel target, as he can be already quite hard to bring down once, and then you have to worry about his second life.
* However, even if Legion Commander does win the duel when Reincarnation is off cooldown, she still receives the permanent victory damage bonus because taking down Wraith King's first life still counts as a "kill".
Pugna
[wiki] rating: 0.6 (winrate: 47% pickrate: 3%)Storm Spirit
* Heroes with mana burn: Nyx Assassin, Invoker, Outworld Destroyer, Pugna, Lion
Legion Commander
* 
Decrepify on either hero stops Legion Commander from completing a Duel, and dissuades her from initiating Duels on ethereal allies.
* 
Life Drain can help Pugna's teammates win a fight, either by killing Legion Commander or replenishing her target's health.
Additional:
* Decrepify prevents Legion Commander from attacking allies during Duel, regardless if it's used on her or on the ally .
* Pugna can easily cast Decrepify, Nether Blast and Life Drain on Legion during the 4/4.75/5.5/8 seconds of duel
Storm Spirit
* Pugna is a very fragile hero who can easily get caught and killed by Storm Spirit's long range initiation.
* This is especially true if he has Orchid Malevolence or Scythe of Vyse.
* Pugna has no disables that can prevent Storm Spirit from escaping.
* Even though Ball Lightning requires high amount of mana, Nether Ward is ineffective since Storm Spirit is invulnerable while using it.
* Storm Spirit's other abilities cost very insignificant amount of mana for Nether Ward to be effective.
Kunkka
[wiki] rating: 0.6 (winrate: 47% pickrate: 3%)Storm Spirit
* In general, highly mobile heroes like 
Earth Spirit or Storm Spirit are at a disadvantage against X Marks the Spot.
* Similarly, heroes with low cooldown teleports can be afraid to split push against X Marks the Spot, such as Tinker and Nature's Prophet.
Lion
[wiki] rating: 0.6 (winrate: 45% pickrate: 10%)Storm Spirit
* Heroes with mana burn: Nyx Assassin, Invoker, Outworld Destroyer, Pugna, Lion
Legion Commander
* Heroes with long or multiple disables will prevent Legion Commander from winning Duels: Shadow Shaman, Lion
Legion Commander
* Lion is extremely dependent on his abilities. Silences like 
Silencer's 
Last Word, magic resistance like Oracle's 
Fate's Edict, and dispels like Legion Commander's Press the Attack all make his abilities less effective.
Razor
[wiki] rating: 0.4 (winrate: 52% pickrate: 7%)Legion Commander
* 
Static Link drains Legion Commander's accumulated damage, effectively neutralizing her overall primary advantage, and prevents her from winning Duels.
* 
Storm Surge's movement speed buff makes Razor and his allies harder to catch and initiate on.
* 
Eye of the Storm, if used beforehand, will always hit Legion Commander during Duels, due to her forced proximity. This drastically lowers her survivability during Duel.
Storm Spirit
* Any hero with teleport abilities (e.g. Ember Spirit, Storm Spirit) can easily break Static Link.
Additional:
* Ball Lightning breaks Static Link.
* Razor has no way to catch a slippery Storm Spirit.
Oracle
[wiki] rating: 0.4 (winrate: 51% pickrate: 4%)Legion Commander
* Fate's Edict prevents Legion Commander from attacking for a few seconds, potentially saving Oracle's ally.
* 
Fortune's End dispels Press the Attack's healing and attack speed buff, as well as the movement speed bonus from Overwhelming Odds.
* 
False Promise protects allies and prevents Legion Commander from winning Duels and gaining bonus damage.
Additional:
* Provided that the enemy team does not have an Axe, Oracle can guarantee that his ally survives for the duration of the Duel with False Promise and has decent nuke potential to help ally to win a Duel. He can also disarm Legion Commander with Fate's Edict.
* Oracle can dispel enemy buffs like Overwhelming Odds and Press the Attack with Fortune's End.
Legion Commander
* Heroes with long disables, like Lion, 
Night Stalker, or Legion Commander, can prevent Oracle from using spells or items.
Slark
[wiki] rating: 0.4 (winrate: 51% pickrate: 17%)Storm Spirit
* Pounce's leash prevents Storm Spirit from using Ball Lightning, making it hard for Storm Spirit to escape a gank from Slark.
* Dark Pact can dispel Orchid Malevolence's Soul Burn.
Storm Spirit
* Heroes that rely on their high mobility such as Queen of Pain, Slark and 
Weaver can be constantly engaged against due to your excellent ability to chase over any terrain. Make sure you carry true sight items (such as 
Dust of Appearance or 
Gem of True Sight) for invisible heroes that could potentially escape your clutches.
Earthshaker
[wiki] rating: 0.4 (winrate: 51% pickrate: 10%)Legion Commander
* Earthshaker's AoE stuns can save ally against Duel, forcing Legion Commander to spend Aghanim's Scepter or Black King Bar.
Storm Spirit
* Heroes with invisibility and high mobility can jump on and focus down Earthshaker before he has a chance to initiate: 
Clinkz, Slark, Storm Spirit
Techies
[wiki] rating: 0.4 (winrate: 48% pickrate: 10%)Storm Spirit
* If Storm Spirit isn't careful, he could fall into a trap set by Techies and another hero acting as bait.
* 
Stasis Trap roots Storm Spirit for 2/3/4/5 seconds and 
Blast Off! silences for 4/5/6/7 seconds, which effectively prevents Storm Spirit from using Ball Lightning to escape for a lengthy duration.
Legion Commander
* Heroes with low health will die easily during Duels, and can be farmed for damage in the early game: 
Crystal Maiden, 
Lich, 
Techies, 
Rubick
Pangolier
[wiki] rating: 0.4 (winrate: 48% pickrate: 9%)Legion Commander
* 
Lucky Shot can disarm Legion Commander and reduce her armor, which can reduce her chances of winning a duel. If an ally is targeted, Pangolier can simply use 
Swashbuckle to inflict it on her.
* If an enemy Pangolier casts a well-timed 
Rolling Thunder before Legion Commander can cast Duel, it might result in her chasing down Pangolier until his or her ultimate ends, whichever duration ends first, resulting in an open window for enemy allies to target Legion Commander, making her vulnerable and susceptible to any source of attacks. If Legion Commander has an Aghanim's Scepter in her inventory, the risk of wasting a solid 8 seconds would result in a futile duel.
* Dueling Pangolier is normally a mistake, Pangolier can disarm you in the duel, and potentially gain some Duel damage, Only duel Pangolier if at least 1 ally is nearby, and he is on low health, And even then, be wary, A good duel can easily turn against you with one Lucky Shot (Due to Lucky Shot lasting 4 seconds).
Additional:
* Swashbuckle can be used to disarm Legion Commander while she is Dueling an ally, granting her opponent a considerable advantage, Lucky Shot lasts 4 seconds at most wasting Legion Commander's entire Duel, (Or half, if Legion Commander has the Scepter).
* Legion Commander will try not to duel Pangolier alone, as she will almost inevitably lose, thanks to Lucky Shot's disarm, If Legion Commander wants to duel a Pangolier, she must be with atleast a teammate, and if she has her scepter, 3 or 4 teammates.
* Legion Commander is often with her allies, allowing you to rack up some considerable damage resistance with Shield Crash.
Storm Spirit
* Heroes with considerable mobility can easily escape from a rolling Pangolier: Anti-Mage, Queen of Pain, 
Void Spirit, Storm Spirit, Ember Spirit, Earth Spirit, moreover, if a player is familiar with how Rolling Thunder works, they can adjust their movement to avoid it entirely and of course outplay the Pangolier player.
Sniper
[wiki] rating: -2.0 (winrate: 44% pickrate: 11%)Storm Spirit
* Storm Spirit can close the distance towards Sniper very easily with his ultimate Ball Lightning.
Additional:
* Sniper is very squishy and cannot deal with heroes that jump onto him and lock him down. Storm Spirit closes the gap in a fight against Sniper, and Sniper has no way to escape except for some items.
* Storm Spirit can dodge 
Assassinate with a correctly timed Ball Lightning.
Legion Commander
* Sniper's low mobility and lack of defensive abilities makes him an easy gank target for the entire game, especially if Blink Dagger is picked up.
Terrorblade
[wiki] rating: -2.0 (winrate: 45% pickrate: 2%)Storm Spirit
* Terrorblade has low mobility, which makes it easy for Storm Spirit to kite him.
* Terrorblade gains a lot of agility and gains very low strength, which makes it easy to burst him down with Storm's magical damage.
* All of Terrorblade's abilities are easily avoided by Storm Spirit as he can simply use Ball Lightning, wasting the duration of 
Metamorphosis, 
Conjure Image, and 
Reflection.
* However, if Storm Spirit's Orchid Malevolence is on cooldown or if he doesn't have it, Terrorblade can easily use 
Sunder and kill a careless Storm Spirit.
Additional:
* Storm Spirit has heavy magic damage that bypasses Terroblade's high armor.
* Ball Lightning can either use to initiates Terroblade from distance or kite Terroblade from using Sunder as he has no source of disable to deal with Storm Spirit.
Legion Commander
* Duel's long duration prevents Terrorblade from swapping his health with Sunder.
* Overwhelming Odds deals high damage to Terrorblade's illusions.
Viper
[wiki] rating: -2.0 (winrate: 49% pickrate: 4%)Storm Spirit
* Ball Lightning allows Storm Spirit to escape through 
Viper Strike, wasting Viper's mana.
* It's also very easy to wait out the duration of 
Nethertoxin's break.
Legion Commander
* Viper's frailty and low mobility makes him an enticing Duel target and 
Corrosive Skin doesn't protect him against Legion Commander physical attacks.
* Press the Attack can dispel 
Poison Attack.
* Viper slows can easily negate by Overwhelming Odds movement speed.
Weaver
[wiki] rating: -2.0 (winrate: 50% pickrate: 3%)Storm Spirit
* Ball Lightning allows Storm Spirit to close the gap between him and Weaver in no time. Once locked down with certain items, Weaver is extremely fragile to Storm Spirit and his teammates.
Legion Commander
* Duel's long duration prevents Weaver from activating 
Time Lapse or escaping with 
Shukuchi.
Broodmother
[wiki] rating: -2.0 (winrate: 54% pickrate: 3%)Storm Spirit
* Ball Lightning and Electric Vortex will catch Broodmother before she has a chance to retreat, and is able to catch her through the trees.
* Conversely, Ball Lightning also allows him to easily escape Broodmother, as she has no way to prevent him from using it before getting Orchid Malevolence.
Legion Commander
* Overwhelming Odds's damage stacks with each enemy unit in its radius. If this hits Broodmother and a large number of spiders it can deal significant amounts of damage.
* Moment of Courage has a high chance to proc if Broodmother and all of her spiders are attacking her.
* Duel can keep Broodmother in place long enough for Legion's team to kill her.
Additional:
* Overwhelming Odds is great at killing many stacked up spiderlings, thus giving Legion Commander a large buff.
* Duel is a reliable way to lock down Broodmother, preventing her from running into the treeline.
Juggernaut
[wiki] rating: -1.6 (winrate: 50% pickrate: 11%)Storm Spirit
* Heroes with escaping and disjointing abilities can be good against Juggernaut:Anti-Mage Riki, Queen of Pain, 
Puck, Storm Spirit, Ember Spirit, Slark etc.
Legion Commander
* Duel pierces spell immunity and forces him to attack Legion Commander, making him unable to use 
Omnislash.
Phantom Lancer
[wiki] rating: -1.6 (winrate: 50% pickrate: 2%)Storm Spirit
* Storm Spirit has multiple AoE abilities to deal with Phantom Lancer, especially with Aghanim's Scepter.
* Ball Lightning destroys illusions, avoids Spirit Lance, and makes Storm Spirit very hard to catch, even with Phantom Rush.
Additional:
* Ball Lightning with or without the Static Remnant talent allows Storm Spirit to destroy Phantom Lancer's illusions quickly. It is also easy to dodge 
Spirit Lance with Ball Lightning and makes Spirit Storm very hard to catch even with 
Phantom Rush.
Legion Commander
* Heroes who rely on illusions will see them destroyed easily by Overwhelming Odds: Phantom Lancer, Chaos Knight, Terrorblade, Naga Siren
Additional:
* Overwhelming Odds deals high damage to Phantom Lancer's illusions.
* Duel's long duration prevents Phantom Lancer from using Doppelganger.
Huskar
[wiki] rating: -1.6 (winrate: 53% pickrate: 6%)Storm Spirit
* Ball Lightning, if timed correctly, and in the right place, can drag Huskar using Life Break all the way to fountain. Or you could also lure him on top of a pillar or into a techies minefield.
Legion Commander
* Carries that can out damage Huskar will do well against him: Legion Commander, Faceless Void, Troll Warlord, Phantom Assassin.
Additional:
* 
Life Break is almost suicidal when used on Legion Commander, as it invites an instant Duel and Legion Commander herself is a natural Blade Mail carrier.
* Huskar's low survivability and mostly on low health makes him particularly vulnerable to Legion Commander's high physical damage.
Tinker
[wiki] rating: -1.4 (winrate: 56% pickrate: 11%)Legion Commander
* Heroes with abilities that blind or cause Legion Commander to miss will prevent her from winning Duels: Arc Warden, Keeper of the Light, Riki, Tinker
Storm Spirit
* Storm Spirit destroys trees and ignores impassable terrains with Ball Lightning, rendering them dangerous places for Tinker to hide within.
* Ball Lightning disjoints projectile from 
Heat-Seeking Missile and damage from 
March of the Machines.
* Electric Vortex prevents Tinker from teleporting away, and Static Remnant and Overload can easily burst him down.
Additional:
* He can easily catch Tinker in the trees with Ball Lightning and kill him with Orchid Malevolence and his abilities, which deal both physical and magical damage, making them difficult for Tinker to itemize against.
Legion Commander
* Press the Attack can dispel Laser's blind while providing great attack speed and health regeneration.
* Once caught in a Duel, Tinker, who completely relies on his spells to be effective, has little chances of survival with his low health pool and armor.
Venomancer
[wiki] rating: -1.2 (winrate: 50% pickrate: 4%)Storm Spirit
* Squishy heroes or heroes without hard disables or silences: Shadow Demon, 
Shadow Fiend, 
Venomancer, Ancient Apparition etc.
Legion Commander
* Heroes rely on their debuff to control the opponent will have a hard time against Press the Attack: Venomancer, Earth Spirit, 
Ogre Magi
Additional:
* Press the Attack dispels Venomous Gale and Poison Sting from Legion Commander or her teammates.
* Venomancer is an ideal target for Duel due to his lack of mobility and low starting health.
Bounty Hunter
[wiki] rating: -1.2 (winrate: 51% pickrate: 7%)Storm Spirit
* Heroes that are naturally hard to gank, ranging from beefy tanks like 
Abaddon and Wraith King to heroes with quick escape mechanisms like Anti-Mage and Storm Spirit are also undesirable targets for a lone, roaming Bounty Hunter to scout out and initiate on.
Legion Commander
* Legion Commander with Press the Attack
* Heroes that can remove the Track debuff with their skills:
* Abaddon with Aphotic Shield and Borrowed Time
* 
Huskar with Life Break
* 
Juggernaut with 
Blade Fury
* Legion Commander with Press the Attack
* 
Lifestealer with 
Rage and 
Infest
* Naga Siren with 
Mirror Image
* Omniknight with 
Heavenly Grace
* Oracle with Fortune's End and False Promise
* Phantom Lancer with 
Doppelganger
* Slark with 
Dark Pact
* 
Ursa with 
Enrage
* Weaver with Time Lapse
* 
Tidehunter with 
Kraken Shell when damage received reaches the threshold.
Bristleback
[wiki] rating: -1.0 (winrate: 43% pickrate: 1%)Legion Commander
* Duel makes Bristleback fight Legion Commander face to face, forcing him to take full damage.
* Press the Attack dispels the slow from stacks of Viscous Nasal Goo.
Additional:
* When dueled, Bristleback will have to face Legion head on, not allowing his passive 
Bristleback to come into effect.
Timbersaw
[wiki] rating: -1.0 (winrate: 46% pickrate: 5%)Storm Spirit
* Ball Lightning makes Storm Spirit a target difficult to chase, even for a hero as mobile as Timbersaw.
* The magical damage from Static Remnant and Overload together with Storm Spirit's high mobility allows Storm Spirit to jump on Timbersaw and burst him down, even if he tries to escape.
Queen of Pain
[wiki] rating: -1.0 (winrate: 46% pickrate: 6%)Storm Spirit
* Once you farm up an Orchid Malevolence or a Scythe of Vyse, you're suddenly a lot more fearsome to elusive heroes like Storm Spirit or even that pesky Puck.
Storm Spirit
* Heroes that rely on their high mobility such as Queen of Pain, Slark and Weaver can be constantly engaged against due to your excellent ability to chase over any terrain. Make sure you carry true sight items (such as Dust of Appearance or Gem of True Sight) for invisible heroes that could potentially escape your clutches.
Legion Commander
* Duels prevents Queen of Pain from using Blink, which may force her to purchase a 
Linken's Sphere
* Because Queen of Pain is also not a right-click hero, Legion won't have much difficulties in duels.
* Press the Attack dispels Shadow Strike's debuff.
Nature's Prophet
[wiki] rating: -1.0 (winrate: 46% pickrate: 12%)Legion Commander
* Heroes with global abilities can give Legion Commander's opponent an edge in Duels from anywhere on the map: Nature's Prophet, Ancient Apparition, Zeus, Invoker, Treant Protector
Storm Spirit
* Ball Lightning can be used to clear Nature's Prophet's Treants and easily destroys Sprout.
* Electric Vortex prevents Nature's Prophet's escaping using Teleportation.
Legion Commander
* Legion Commander's Overwhelming Odds deals damage for every Treant it hits, which allows it to easily wipe out large waves of them.
Shadow Demon
[wiki] rating: -1.0 (winrate: 47% pickrate: 1%)Legion Commander
* Heroes who can hide the Dueled target (Outworld Destroyer, Shadow Demon, Tusk, Phoenix with Aghanim's Scepter etc).
Additional:
* Disruption can save allies and mess up an initiation from an enemy Legion Commander. Using Disruption on your ally that is affected by Duel will leave her totally exposed without the benefit of the life steal from Moment of Courage. A precise decision to Disrupt Legion Commander or her victim is crucial to waste Duel's potential.
* Demonic Purge cannot be dispelled by a hard dispel from Press the Attack, which in turn can be dispelled by your ultimate.
Storm Spirit
* Shadow Demon will have a hard time catching Storm Spirit, as he can get away with Ball Lightning.
* Static Remnant will make quick work of the spawned illusions from Disruption.
* With very high mobility and usually being paired with Orchid Malevolence, he can catch Shadow Demon with ease both in ganks and in teamfights if Shadow Demon has no survivability items.
Legion Commander
* Heroes who can dispel will be able to remove remove Soul Catcher's debuff to instantly bring the health of affected heroes back to a considerable amount: Abaddon, Slark, Legion Commander, Oracle.
Hoodwink
[wiki] rating: -1.0 (winrate: 47% pickrate: 13%)Storm Spirit
* Storm Spirit can easily make his way to Hoodwink with his ultimate Ball lightning, and coupled with Hoodwink's low health and magic resistance, she can be nuked easily.
* Additionally, Ball lightning can destroy a small amount of trees in its destination. Combined with Storm Spirit's frequent usage of his ultimate, he can clear out an area of trees while simultaneously attacking him and dodging incoming attacks.
Batrider
[wiki] rating: -1.0 (winrate: 48% pickrate: 5%)Legion Commander
* Press the Attack dispels Flaming Lasso.
* Batrider is unlikely to win a Duel in any stage of the game.
Bloodseeker
[wiki] rating: -1.0 (winrate: 49% pickrate: 3%)Storm Spirit
* Storm Spirit is invulnerable during Ball Lightning, allowing him to zip away from any ganking attempts with Rupture.
* Ball Lightning also prevents Bloodseeker from chasing down an injured Storm Spirit, or catching him in Blood Rite.
Additional:
* Storm Spirit is invulnerable during Ball Lightning, rendering 
Rupture ineffective against him.
Keeper of the Light
[wiki] rating: -1.0 (winrate: 49% pickrate: 3%)Legion Commander
* Heroes with abilities that blind or cause Legion Commander to miss will prevent her from winning Duels: Arc Warden, Keeper of the Light, Riki, Tinker
Storm Spirit
* Heroes with teleports to escape Solar Blind and Will-O-Wisp: Phantom Assassin, Puck, Queen of Pain, Storm Spirit
Legion Commander
* Press the Attack can dispel Blinding Light or Solar Bind from a hero.
* Duel can be used to instantly take Keeper of the Light out of a team-fight.
Crystal Maiden
[wiki] rating: -1.0 (winrate: 49% pickrate: 13%)Legion Commander
* Duel is a great initiation to target Crystal Maiden with, as it prevents her from using Freezing Field or any other abilities and allowing the enemy team to quickly kill her before she can aid her team in a fight.
Pudge
[wiki] rating: -1.0 (winrate: 49% pickrate: 29%)Legion Commander
* Legion Commander can use Press the Attack on an ally to dispel Dismember. The bonus health regeneration also partially counters the damage of Rot
* Duel can be used on Pudge whilst Rot is active, disabling toggling which may result in a lethal health drain that leaves Legion Commander with a successful duel.
Vengeful Spirit
[wiki] rating: -1.0 (winrate: 49% pickrate: 5%)Storm Spirit
* Ball Lightning disjoints an incoming 
Magic Missile, avoids 
Wave Of Terror, and allows Storm Spirit to easily escape if he ever gets 
Nether Swapped.
Primal Beast
[wiki] rating: -1.0 (winrate: 49% pickrate: 9%)Legion Commander
* Duel prevents Primal Beast from using all of his spells and stops all of his damage output.
* Moment of Courage will not proc if Primal Beast is using Trample so you may want to play around that if you're looking for duel damage with a Blade Mail.
* Press the Attack can be used to dispel Pulverize immediately and make allies survive Trample for a short duration with the heal.
Drow Ranger
[wiki] rating: -1.0 (winrate: 51% pickrate: 18%)Legion Commander
* Drow Ranger's low mobility and lack of defensive abilities makes her an easy gank target in the early to mid-game.
* A Dueling Drow Ranger will lose her precious 
Marksmanship, reduce her damage output significantly and will more likely lose that Duel.
Dark Willow
[wiki] rating: -1.0 (winrate: 51% pickrate: 4%)Storm Spirit
* Ball Lightning allow Storm Spirit to bypass Bramble Maze, and zip back into battle if he gets hit by Terrorize.
Chen
[wiki] rating: -1.0 (winrate: 51% pickrate: 0%)Legion Commander
* Chen's fragility and low mobility make him an enticing Duel target.
* Overwhelming Odds and Moment of Courage can take advantage of converted creeps' numbers.
* With enough damage from Duel stacks, Legion Commander can also often kill any of Chen's unfortunate allies before he can use Hand of God.
Additional:
* Chen's frailty and low mobility make him an enticing Duel target.
* Overwhelming Odds and Moment of Courage can take advantage of converted creeps' numbers.
* With enough damage from Duel stacks, Legion Commander can also often kill any of Chen's unfortunate allies before he can use 
Hand of God.
Spectre
[wiki] rating: -1.0 (winrate: 51% pickrate: 11%)Storm Spirit
* Storm Spirit can exploit every one of Spectre's weaknesses, and thus is one of the best counters against her.
* Spectre has to be in melee range to deal damage, making her likely to trigger Static Remnants and susceptible to being kited by Overload procs.
* Electric Vortex can lock Spectre down as she doesn't like to build Black King Bar.
* Ball Lightning gives Storm Spirit multiple advantages:
* Spectre cannot evade Storm Spirit, as Ball Lightning is superior to 
Spectral Dagger in terms of mobility.
* Storm Spirit can kite her and her 
Haunt illusions when it's later in the game due to her having no form of pseudo-blinks (Reality is far inferior to Ball Lightning).
* It is very difficult for Spectre to deal any substantial damage against Storm Spirit with 
Desolate. Ball Lightning grants invulnerability and can mitigate damage done from 
Dispersion and 
Radiance.
* To mitigate this, Spectre needs a team with hard disable to take Storm Spirit out.
Additional:
* Ball Lightning is the ultimate counter to Spectre's entire toolkit. With this ability, he can score easy kills on Spectre without her having any means of escape early game, kite her and her Haunt illusions when it's later in the game due to her having no form of pseudo-blinks.
* Furthermore, it is very difficult for Spectre to deal any substantial damage against Storm Spirit with Desolate, and without both 
Manta Style and 
Diffusal Blade he will always remain on the move.
* Also, Ball Lightning grants invulnerability, and as Storm Spirit likes to spam that ability, he can mitigate the damage done from Dispersion and Radiance.
Clinkz
[wiki] rating: -1.0 (winrate: 52% pickrate: 7%)Legion Commander
* 
Searing Arrows and Clinkz physical damage items is almost suicidal when used on Legion Commander, as it invites an instant Duel and Legion Commander herself is a natural Blade Mail carrier.
* Duel locks down Clinkz for a long duration, preventing him from escaping with 
Skeleton Walk.
Muerta
[wiki] rating: -0.6 (winrate: 45% pickrate: 13%)Storm Spirit
* Gap closers (Storm Spirit, Pudge) can easily kill Muerta.
Grimstroke
[wiki] rating: -0.6 (winrate: 46% pickrate: 4%)Storm Spirit
* Heroes with mobility spells can quickly escape from Stroke of Fate or break out of Soulbind: Anti-Mage, Queen of Pain, 
Morphling, Storm Spirit
Mars
[wiki] rating: -0.6 (winrate: 46% pickrate: 10%)Legion Commander
* Because Duel requires both combatants to face each other, 
Bulwark's effectiveness will be increased by a huge margin, which makes it much more difficult for Legion Commander to win any duels against him.
* 
Spear of Mars and 
God's Rebuke pushes Legion Commander away during Duels against allies.
Additional:
* Bulwark immensely mitigates Duel, even with bonus physical damage, as Bulwark scales by percentage. Mars can also buy time for a dueled ally by pushing Legion Commander away with Spear of Mars.
Storm Spirit
* Ball Lightning makes it almost impossible to catch Storm Spirit without someone else initiating for you.
* Overload is not reduced by Bulwark and the magical damage spam can wear down Mars quickly.
Additional:
* Storm Spirit's abilities all do magical damage, which can bypass Bulwark.
* Ball Lightning can escape through 
Arena of Blood and it is easy to dodge Spear of Mars.
Legion Commander
* Legion Commander is both good and bad vs Mars, on the plus side she can dispel Spear of Mars with Press the Attack and is a good Silver Edge carrier. However, Mars is not an ideal Duel target, as Bulwark will force her to 1: Buy Silver Edge, and 2: Hit Mars with it before the Duel, allowing a skilled Mars to react, especially with Eul's Scepter of Divinity. In teamfights, Mars will happily draw attention after using his abilities, and tank the Duel with all spells on cooldown.
Rubick
[wiki] rating: -0.6 (winrate: 47% pickrate: 25%)Legion Commander
* Heroes with low health will die easily during Duels, and can be farmed for damage in the early game: Crystal Maiden, Lich, Techies, Rubick
Chaos Knight
[wiki] rating: -0.6 (winrate: 47% pickrate: 3%)Legion Commander
* Heroes with strong area damage to destroy Phantasm illusions: Axe, Ember Spirit, Legion Commander, Phoenix
Marci
[wiki] rating: -0.6 (winrate: 48% pickrate: 7%)Storm Spirit
* Heroes that can reliably kite out Dispose, Unleash and dodge Rebound, like Ember Spirit, Void Spirit, Storm Spirit, Anti-Mage, Faceless Void, Puck or always build items like Blink Dagger and 
Force Staff.
Shadow Fiend
[wiki] rating: -0.6 (winrate: 48% pickrate: 18%)Storm Spirit
* Squishy heroes or heroes without hard disables or silences: Shadow Demon, Shadow Fiend, Venomancer, Ancient Apparition etc.
Void Spirit
[wiki] rating: -0.6 (winrate: 48% pickrate: 5%)Legion Commander
* Special mention to Legion Commander, as she can lock down Void Spirit for a long amount of time without worrying too much about being killed by him during the Duel.
Ogre Magi
[wiki] rating: -0.6 (winrate: 48% pickrate: 7%)Legion Commander
* Heroes rely on their debuff to control the opponent will have a hard time against Press the Attack: Venomancer, Earth Spirit, Ogre Magi
Spirit Breaker
[wiki] rating: -0.6 (winrate: 48% pickrate: 9%)Storm Spirit
* Heroes that usually builds Linken's Sphere as a core item: Weaver, Medusa, Morphling, Queen of Pain, Storm Spirit
Lifestealer
[wiki] rating: -0.6 (winrate: 49% pickrate: 5%)Storm Spirit
* Heroes with escape abilities : Anti-Mage 
Dark Seer Slark Storm Spirit 
Windranger Weaver can kite Lifestealer due to him having no lockdown
Earth Spirit
[wiki] rating: -0.6 (winrate: 49% pickrate: 3%)Legion Commander
* Heroes rely on their debuff to control the opponent will have a hard time against Press the Attack: Venomancer, Earth Spirit, Ogre Magi
Gyrocopter
[wiki] rating: -0.6 (winrate: 50% pickrate: 7%)Storm Spirit
* Heroes with high mobility will be able to avoid Gyrocopter's area attacks: Storm Spirit, Morphling, Ember Spirit
Warlock
[wiki] rating: -0.6 (winrate: 51% pickrate: 4%)Legion Commander
* Heroes who rely on summons will see them destroyed easily by Overwhelming Odds: Lycan, Arc Warden, 
Warlock, 
Chen
Lich
[wiki] rating: -0.6 (winrate: 51% pickrate: 9%)Legion Commander
* Heroes with low health will die easily during Duels, and can be farmed for damage in the early game: Crystal Maiden, Lich, Techies, Rubick
Io
[wiki] rating: -0.6 (winrate: 51% pickrate: 4%)Legion Commander
* 
Tethered heroes are much harder for Legion Commander to kill in Duels.
* 
Relocate can cancel Duels and save allies.
Storm Spirit
* Heroes that can easily bypass Io's allies to get to Io: Riki, Tusk, Clinkz, 
Sniper, Slark, Phantom Assassin, Void Spirit, Storm Spirit, Ember Spirit, Earth Spirit, 
Spirit Breaker.
Legion Commander
* Duel is very effective against Io due to its low health and armor.
Arc Warden
[wiki] rating: -0.6 (winrate: 53% pickrate: 5%)Legion Commander
* Magnetic Field prevents Legion Commander from getting wins with Duel.
Additional:
* 
Magnetic Field prevents Legion Commander from easily gaining wins with Duel.
Storm Spirit
* Storm Spirit can hunt down Arc Warden with his Ball Lightning and kill him quickly due to his lack of escape abilities.
* None of his abilities are effective against Storm Spirit, as they can be evaded with Ball Lightning.
Legion Commander
* Heroes who rely on summons will see them destroyed easily by Overwhelming Odds: Lycan, Arc Warden, Warlock, Chen
Mirana
[wiki] rating: -0.6 (winrate: 53% pickrate: 15%)Legion Commander
* Heroes that cannot move in fights such as a Dueling Legion Commander or anyone channeling a spell like 
Bane, Pudge, or 
Enigma are easy Sacred Arrow targets.
Storm Spirit
* Heroes that have superior mobility that can easily catch up with Mirana even after she used Leap to escape: Anti-Mage, Queen of Pain, Storm Spirit, Riki.
Legion Commander
* Heroes that can protect or dispel stunned allies such as Legion Commander, Outworld Destroyer, Shadow Demon and Oracle can reduce the effectiveness of Sacred Arrow.
Lycan
[wiki] rating: -0.6 (winrate: 57% pickrate: 3%)Legion Commander
* Heroes who rely on summons will see them destroyed easily by Overwhelming Odds: Lycan, Arc Warden, Warlock, Chen
Monkey King
[wiki] rating: -0.4 (winrate: 47% pickrate: 8%)Legion Commander
* Heroes that lack burst damage will have a difficult time taking down Monkey King, and fare badly against Jingu Mastery: Legion Commander, Lifestealer, Weaver, Wraith King
Storm Spirit
* Ball Lightning allows Storm Spirit to easily catch up to Monkey King, destroying a large number of trees, cancelling Tree Dance, and causing Monkey King to be stunned in the process.
Additional:
* Ball Lightning allows Storm Spirit to destroy a large amount of trees, negating 
Tree Dance. It also makes it easy to avoid 
Wukong's Command and 
Boundless Strike.
Enigma
[wiki] rating: -0.4 (winrate: 50% pickrate: 3%)Legion Commander
* Enigma can be a perfect counter-initiator with his ultimate. A perfectly timed Black Hole will turn the tide of any initiation, especially from heroes like; Spirit Breaker, Legion Commander, Axe, Puck, and 
Slardar
Storm Spirit
* An isolated Enigma in the early game can be easily killed by Storm Spirit thanks his higher mobility and dueling potential. However, Storm Spirit can be killed when caught by Enigma's full combo, especially if Enigma has Black King Bar.
* Storm can kill all of Enigma's Eidolons relatively quickly without much risk, slowing down Enigma's farming speed, preventing him from split pushing, and giving Storm its considerable bounty, especially if Enigma chooses the Level 25 Talent that gives him more Eidelons.
* Storm can zip through 
Black Hole stunning Enigma while he's channelling until Enigma buys Black King Bar.
Death Prophet
[wiki] rating: -0.4 (winrate: 55% pickrate: 11%)Storm Spirit
* Any heroes with stuns or silences: 
Death Prophet, Lion, Shadow Shaman, 
Skywrath Mage
Legion Commander
* Duel is a great initiation to kill Death Prophet before she can cast Exorcism. Furthermore, Legion Commander often builds Blade Mail and can reflect Exorcism's damage to kill Death Prophet easily.
Luna
[wiki] rating: -0.2 (winrate: 49% pickrate: 2%)Legion Commander
* A well-timed 
Eclipse before a Duel usually prevents Legion Commander from winning Duels, if Luna is the target.
* Meanwhile, when Luna is not a target, Eclipse and 
Lucent Beam can also help an ally win a Duel against Legion Commander.
* However, skilled Legion Commander will always buy a Black King Bar to block Eclipse and Lucent Beam or Aghanim's Scepter to reduce it's damage.
Additional:
* A well-timed Eclipse before a Duel usually prevents Legion Commander from winning Duels if Luna is the target. Luna can also buy Linken's Sphere to block Duel.
* Meanwhile, when Luna is not a target, Eclipse and Lucent Beam can also help an ally win a Duel against Legion Commander.
* Bear in mind, however, that skilled Legion Commander will always buy a Black King Bar to block Eclipse and Lucent Beam or Aghanim's Scepter to reduce their damage.
Storm Spirit
* Escape-type carries: Slark, Storm Spirit, Weaver.
Legion Commander
* Heroes that can keep Luna locked down for a long time can be a threat (she is very item and spell dependent): Faceless Void, Legion Commander, 
Doom.
Invoker
[wiki] rating: 0.0 (winrate: 48% pickrate: 14%)Storm Spirit
* Heroes with mana burn: Nyx Assassin, Invoker, Outworld Destroyer, Pugna, Lion
Legion Commander
* Invoker's spells will disable and destroy Legion Commander while she's locked in a Duel.
Storm Spirit
* In the early to mid game, Invoker is defenseless against Storm Spirit's ganking with Ball Lightning and Orchid Malevolence.
Legion Commander
* Heroes with long lockdowns: Shadow Shaman, Legion Commander.
Ember Spirit
[wiki] rating: 0.0 (winrate: 48% pickrate: 11%)Storm Spirit
* 
Flame Guard absorbs up to 500 magical damage (700 with Level 10 talents), which helps Ember Spirit survive against Storm Spirit's high magical damage.
* 
Searing Chains can root enemies up to 3 seconds, making Storm Spirit unable to escape with Ball Lightning.
* 
Fire Remnant deals high magical damage when casting multiple instances at once, granting Ember Spirit the damage to burst Storm Spirit down in the early to mid game.
Storm Spirit
* Storm Spirit is not only a potent Orchid Malevolence carrier, his Electric Vortex provides an additional disable and Overload provides a great slow. When paired with Static Remnant, they can cut through Flame Guard fast.
* Ball Lightning not only provides great initiation upon Ember Spirit from any position anytime, but also helps dodge Sleight of Fist.
Zeus
[wiki] rating: 0.0 (winrate: 49% pickrate: 14%)Legion Commander
* Heroes with global abilities can give Legion Commander's opponent an edge in Duels from anywhere on the map: Nature's Prophet, Ancient Apparition, Zeus, Invoker, Treant Protector
Storm Spirit
* Zeus can deal a huge amount of damage, but he lacks defensive abilities, such as good mobility or resistance. Due to that, he doesn't like to be touched by any means. Heroes with higher damage output and good mobility will often get easily near Zeus and trade damage (eventually causing Zeus's downfall). Such Heroes include: Lycan, Slark, Storm Spirit, 
Spectre and others.
Nyx Assassin
[wiki] rating: 0.0 (winrate: 50% pickrate: 4%)Storm Spirit
* Mana Burn removes much-needed mana for Ball Lightning.
* Spiked Carapace triggers on Static Remnant for an easy stun.
Additional:
* 
Mana Burn is capable of removing most of Storm Spirit's large mana pool, along with dealing heavy damage and quickly depleting his chances of escaping a gank or fight.
Legion Commander
* Duel's long duration prevents Nyx Assassin escaping from 
Vendetta. With Aghanim's Scepter she can also bypasses 
Spiked Carapace.
Ancient Apparition
[wiki] rating: 0.0 (winrate: 50% pickrate: 5%)Legion Commander
* Heroes with global abilities can give Legion Commander's opponent an edge in Duels from anywhere on the map: Nature's Prophet, Ancient Apparition, Zeus, Invoker, Treant Protector
Storm Spirit
* Heroes with mobility/escape mechanisms to dodge Ancient Apparition abilites, or to easily jump on him: Riki, Queen of Pain, Phantom Assassin, Windranger, 
Bounty Hunter, Spirit Breaker, Night Stalker, Storm Spirit, Juggernaut, etc.
Additional:
* Ancient Apparition's only skill to stop Storm Spirit is 
Cold Feet, which is bad in general when trying to stop a Storm Spirit without any other disable.
* As a fragile support with low Strength gain and no magic resistance, Ancient Apparition is vulnerable to Storm Spirit's combos.
Beastmaster
[wiki] rating: 0.0 (winrate: 51% pickrate: 2%)Storm Spirit
* Heroes who rely on high mobility are especially vulnerable to Primal Roar: Storm Spirit, Ember Spirit, Queen of Pain.
Storm Spirit
* Heroes with AoE abilities are a bane to Beastmaster's summons: Storm Spirit, Magnus, 
Pangolier.
Ursa
[wiki] rating: 0.0 (winrate: 52% pickrate: 15%)Legion Commander
* 
Fury Swipes can give Ursa the edge in Duels.
* Enrage's instant cast time allows it to be used before Legion Commander initiates a Duel, causing Ursa to take almost no damage for a brief period of time.
* However, Duel stops Ursa from casting Enrage at the most critical moment
Storm Spirit
* Storm Spirit can steal 
Aegis of the Immortal during Roshan attempts through the Pit, because of his Ball Lightning.
* Ursa has no way to catch a slippery Storm Spirit, as Earthshock's slow will do nothing to stop Storm Spirit from using Ball Lightning.
Silencer
[wiki] rating: 0.0 (winrate: 52% pickrate: 15%)Storm Spirit
* Basically, Heroes that heavily rely on abilities for damage or escape, such as Queen of Pain and Storm Spirit.
Additional:
* Silencer's 
Intelligence Steal can reduce Storm Spirit's damage output if he gets some kills on laning phase.
* Last Word and 
Global Silence will make Storm Spirit an easy target.
* Global Silence can be used to prevent Storm Spirit from connecting abilities after a Ball Lightning on his targets.
Legion Commander
* Heroes that can disable or silence Silencer for a long time, such as Bane and Legion Commander, can lock down Silencer while their allies put him down.
Anti-Mage
[wiki] rating: 0.0 (winrate: 53% pickrate: 11%)Storm Spirit
* Because of the high mana cost of Ball Lightning, Storm Spirit is often vulnerable to Mana Void.
* Mana Break diminishes Storm Spirit's mobility with Ball Lightning, and Anti-Mage can catch him with Blink over short distances.
* Almost all of Storm Spirit's damage is magical, which is severely reduced by Counterspell.
* Storm Spirit has a very large mana pool which means Anti-Mage can do large amounts of damage to him with Mana Break and Mana Void.
Additional:
* 
Mana Break can quickly burn Storm Spirit's mana, preventing him from escaping.
* 
Blink allows Anti-Mage to catch up to Storm Spirit when he tries to use his Ball Lightning to escape.
* 
Mana Void deals massive damage to Storm Spirit as well as his teammates, as Storm Spirit depletes his mana pool by using Ball Lightning.
* 
Counterspell's passive magic resistance reduces much of Storm Spirit's magical damage dealt to Anti-Mage, and the active aspect may even make Storm Spirit disable himself.
Legion Commander
* Duel renders Anti-Mage's escape capabilities with Blink and Counterspell useless. Blade Mail and Moment of Courage work well against Anti-Mage's relatively low health.
* A good initiation from Legion Commander and her team is enough to effortlessly kill Anti-Mage.
Additional:
* Counterspell offer no protection against Duel at all.
* Duel locks down Anti-Mage for a long duration, preventing him from escaping with Blink. One successful Duel initiation is usually enough for Legion Commander's team to kill Anti-Mage.
Storm Spirit
* Earthbind, like any root, inhibits usage of
Ball Lightning, eliminating Storm Spirit's mobility.
Legion Commander
* When Legion Commander uses
Duel on one Meepo, he can use his other Meepos to kill her. If he wasn't dueled, he can help the teammate who was duelled to give the teammate the damage instead of Legion Commander.
* However, if Legion Commander picked up an Aghanim's Scepter and she duels one Meepo, that might be the end of Meepo if Legion managed to gather enough damage from previous duels.