Riki
* Riki takes a lot of damage from 
Purification while ganking Omniknight's allies or himself.
* 
Heavenly Grace instantly purges the slow from 
Diffusal Blade, while also providing a large amount of survivability for his victim.
* 
Degen Aura can hinder Riki's positioning tactics and put a heavy toll on Riki's already poor movement speed.
* Omniknight can easily save his allies by using 
Guardian Angel in combat.
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.
Riki
* 
Static Link drains away Riki's damage while keeping his location revealed for its duration, allowing his team to accurately land detection or area-of-effect skills.
* 
Storm Surge procs on invisible heroes, making him aware of Riki's presence near him.
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.
* 
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.
Riki
* 
Pit of Malice prevents Riki from casting 
Blink Strike. or 
Tricks of the Trade.
* 
Atrophy Aura reduces Riki's damage.
* 
Firestorm can be used to harrass Riki in lane.
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.
Riki
* Heroes with high mobility can be prevented from using it to their advantage with Earthbind, even if they pack a dangerous arsenal: 
Earth Spirit, 
Ember Spirit, 
Storm Spirit, 
Nature's Prophet, 
Phantom Assassin, 
Riki, 
Anti-Mage, 
Weaver.
* See items and abilities disabled by roots
Additional:
* Root is a deadly threat to Riki, disabling both Blink Strike and Tricks of the Trade while making him fully revealed, making 
Earthbind a good ability against him.
* 
Smoke Screen may not be able to silence all the Meepo clones.
* Riki has no true area damage, as Tricks of the Trade's damage is distributed between all Meepo clones, so he cannot effectively fight Meepo or deal with his strong ability to push unless Riki has 
Battle Fury.
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.
Riki
* Heroes who are reliant on physical damage will be nullified by Decrepify: Riki, 
Wraith King, 
Juggernaut.
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
Riki
* Zeus's 
Lightning Bolt and 
Thundergod's Wrath provides a short duration of True Sight, revealing Riki while possibly dealing a heavy amount of damage.
* Zeus's 
Nimbus can be placed directly on top of Tricks of the Trade, potentially causing him to be damaged, stunned, and revealed the instant he becomes targetable again.
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
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.
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.
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.
Riki
* Low-health, normally mobile carries who rely entirely on raw attack damage are vulnerable to Bane's nukes and disables: Anti-Mage, 
Clinkz, 
Drow Ranger, 
Faceless Void, 
Gyrocopter, Juggernaut, 
Meepo, 
Mirana, 
Monkey King, 
Morphling, Phantom Assassin, 
Phantom Lancer, Riki, 
Shadow Fiend, 
Slark, 
Sniper, 
Terrorblade, 
Troll Warlord, Weaver.
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.
Riki
* Thirst detects Riki whenever his health is low.
* Rupture does large damage when Riki uses Blink Strike.
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.
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.
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.
Legion Commander
* Solar Guardian can save allies who are being dueled and will interrupt her Duel initiation.
Riki
* With Dark Ascension and Gem of True Sight, Night Stalker can easily find and kill Riki. Riki will also find it harder to kill the tanky Night Stalker than he would many other heroes.
Riki
* Riki can easily be caught in an Ice Path and Macropyre combo as he finishes Tricks of the Trade, Jakiro just has to be careful about Riki's Smoke Screen when dealing with Riki.
Riki
* Riki does little damage to Dragon Knight, as he relies only on physical damage with modest attack speed and lack of burst.
Riki
* 
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
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.
Riki
* Blink Strike does not grant Riki a mobility advantage over Phantom Assassin, as her Phantom Strike serves the same purpose, but with a higher range.
* A Carry Riki usually has a hard time dealing with Blur, as a 
Monkey King Bar or 
Bloodthorn are unfavourable item picks for him (or, even more unlikely, a 
Silver Edge).
* A 
Black King Bar is a very common pick for Phantom Assassin, fully countering Smoke Screen and Diffusal Blade while activated.
Riki
* Luna can push very fast with Moon Glaives, which is something Riki cannot deal with well.
* Luna is naturally very fast, making it hard for Riki to trap her in Smoke Cloud.
* Even though Riki can evade 
Eclipse with his invisibility, smart Luna will always buy 
Dust of Appearance, providing vision on Riki to her allies and herself.
Additional:
* Luna can push very fast with Moon Glaives, which is something Riki cannot deal with well.
* Luna is naturally very fast, making it hard for Riki to trap her in Smoke Cloud.
* Even though Riki can evade Eclipse with his invisibility, smart Luna will always buy Dust of Appearance, providing vision on Riki to her allies and herself.
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.
Riki
* All assassin-type carries in a one against one situation: Meepo, Phantom Assassin, Riki, 
Ursa. Luna's only chances are that she buys 
Ethereal Blade or Black King Bar to gain a slight edge against them, or both items if necessary.
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.
Riki
* Riki doesn't deal burst damage.Durable heroes (
Axe, 
Tidehunter etc.) will usually survive a jump from him,move out of Smoke Screen and potentially retaliate.
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.
Riki
* Charge of Darkness provides shared vision over its target, keeping track of heroes who rely on invisibility, mobility, or illusions: Riki, 
Broodmother, Phantom Lancer
Riki
* Heroes with blink or movement abilities, which are disabled by Pounce's leash: Anti-Mage, Earth Spirit, Faceless Void, Magnus, Mirana, Monkey King, Morphling, 
Pangolier, Phantom Assassin, Phoenix, 
Puck, 
Queen of Pain, Riki, 
Sand King, 
Spirit Breaker, 
Timbersaw, Tusk.
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.
Riki
* Heroes who rely on invisibility, such as 
Bounty Hunter, Clinkz, Mirana, 
Nyx Assassin and Riki, as they will be revealed if caught by Chronosphere.
Legion Commander
* Troll Warlord's melee bash and high attack speed can often help him and his allies win Duels against Legion Commander.
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
Riki
* In general, heroes who are melee with no way to fight back can be very easily poked by Monkey King to gain his Jingu Mastery stacks: 
Dark Seer, Riki, 
Rubick.
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
Riki
* Heroes with blind of some sort can be a bad choice for Monkey King to go on: Broodmother, Riki, 
Keeper of the Light.
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.
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.
Legion Commander
* Earthshaker's AoE stuns can save ally against Duel, forcing Legion Commander to spend Aghanim's Scepter or Black King Bar.
Riki
* Earthshaker must be careful not to use Blink Dagger or Aghanim's Scepter upgraded 
Enchant Totem to blink into Riki's Smoke Screen or Night Stalker's 
Crippling Fear, as these field effects will instantly silence Earthshaker and prevent him from initiating.
Riki
* Axe can disable 
Cloak and Dagger's invisibility with 
Berserker's Call, which forces Riki to attack him at a very bad angle.
* Axe has a very high HP pool, making it hard for you to kill him before you get big items - that is if you survive engaging him. 
Counter Helix ignores Riki's armor and goes straight for his tiny HP pool, totally ignoring Smoke Screen.
* Axe is a natural buyer of Blade Mail and Riki generally does not buy lifesteal items, causing Riki to kill himself when attacking due to your tiny HP pool.
Legion Commander
* Long lockdown is a great way to deal with Axe to prevent Berserker's Call from being used, heroes such as Legion Commander, 
Beastmaster and 
Primal Beast are good examples of this.
Riki
* Any hero with a low HP pool is easy for Tinker to nuke down: 
Crystal Maiden, 
Enchantress, Gyrocopter, Lion, Riki, 
Techies, Terrorblade, 
Necrophos, Invoker.
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
* 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.
Riki
* Sniper has no natural escape and relies on his range and slows to keep himself safe, which Riki can bypass with Blink Strike and quickly deplete his miniature HP pool.
Legion Commander
* Sniper's low mobility and lack of defensive abilities make him an easy gank target for the entire game, especially if Blink Dagger is picked up.
Riki
* Smoke Cloud prevents 
Shukuchi and 
Time Lapse, leaving Weaver helpless against Riki.
* 
The Swarm is ineffective against Riki because invisibility instantly removes the beetles.
Legion Commander
* Duel's long duration prevents Weaver from activating Time Lapse or escaping with Shukuchi.
Riki
* Smoke Cloud prevents Queen of Pain from using any of her offensive and defensive spells, rendering her unable to effectively react to Riki's attack.
* It's easy to dodge 
Sonic Wave by using Blink Strike & Tricks of the Trade.
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.
Riki
* Blink Strike gets Riki close to Drow Ranger and disable Marksmanship.
* Cloak and Dagger allow Riki stay close to Drow Ranger without her noticing him, which allows him to disable Marksmanship.
Additional:
* With Blink Strike, Riki can get close to Drow Ranger and disable her 
Marksmanship, and Smoke Screen will prevent her from using 
Gust.
Legion Commander
* Drow Ranger's low mobility and lack of defensive abilities make 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.
Riki
* Heroes that can easily bypass Chen's creeps to get to Chen: Riki, Tusk, Clinkz, Sniper, Slark, Phantom Assassin, 
Void Spirit, Storm Spirit, Ember Spirit, Earth Spirit, Spirit Breaker.
Additional:
* Chen is basically Riki's natural prey: he has little HP, low armor and relies on his persuaded creeps to fight, which in most situations will not save Chen from Riki. Just be wary of {U:Centaur Conqueror}, who can stun Riki outside of Smoke Screen and ruin his attempt at Chen's life.
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's 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.
Riki
* Riki has high damage and invisibility, meaning he can easily gank Rubick and kill him before Rubick has the chance to react.
* Cloak and Dagger renders Riki invisible, which makes his spells hard to steal if not being initiated.
* Similar to Clinkz, Rubick has to buy a large amount of Sentry Wards to keep track of Riki due to Cloak and Dagger, preventing Rubick from getting better items.
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
Riki
* Heroes with a high degree of mobility and invisibility are hard to catch with Meat Hook: Ember Spirit, Riki, Clinkz, Queen of Pain.
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.
Riki
* Riki is another good hero to shutdown Death Prophet with Diffusal Blade as his core item. His Smoke Screen stops her from initiating and casting spells.
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.
Riki
* Heroes with abilities or items that can silence or disable Anti-Mage for long periods of time will prevent him from Blinking away: Lion, 
Silencer, 
Shadow Shaman, 
Grimstroke, 
Witch Doctor, Riki, Faceless Void, 
Skywrath Mage, Puck.
Additional:
* Anti-Mage can use neither 
Blink nor 
Manta Style to escape from Smoke Cloud.
* Even if he activates a Black King Bar, his Manta Style illusions will still be blinded by Smoke Cloud.
* Riki has a very small mana pool and generally doesn't buy many items that increase it, making 
Mana Void ineffective.
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.
Riki
* Heroes with high armor like 
Dragon Knight, or with abilities to cause attacks to miss like Phantom Assassin, Riki and Tinker will be hard to deal with, as Clinkz relies almost entirely on physical attacks.
Additional:
* Smoke Cloud prevents the use of 
Death Pact, 
Searing Arrows and 
Skeleton Walk, so Clinkz can neither defend himself against Riki nor fight back effectively.
* It's hard to gank Riki as Clinkz has to find him first.
Legion Commander
* Searing Arrows and Clinkz physical damage items are 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.
Riki
* 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.
Riki
* Frostbite will reveal invisible heroes for its duration, making it a good tool against any such hero (Riki, Bounty Hunter, Weaver, or Clinkz for example), or as a soft counter to 
Shadow Blade, if it is used first. This can be an amazing tool to ensure that Dust of Appearance is used on the unit in question, and not wasted in not catching anything.
Riki
* Smoke Screen effectively disables Crystal Maiden's channeling spell: 
Freezing Field.
* Due to her low health and armor throughout the game, Riki can kill her easily.
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.
Riki
* Warlock is a very strong hero when positioned correctly, and his long cast range helps him with this. However, some heroes might disrupt or sneakily pass through his allies and deal with him, preventing him from doing his job. Such heroes include Chaos Knight, Spirit Breaker, Riki, and more.
Legion Commander
* Heroes who rely on summons will see them destroyed easily by Overwhelming Odds: 
Lycan, Arc Warden, 
Warlock, 
Chen
Riki
* Heroes with damage-increasing passive abilities, such as 
Viper and Riki, will usually kill Silencer in a short time before he even has time to set up his abilities.
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.
Legion Commander
* Press the Attack dispels Flaming Lasso.
* Batrider is unlikely to win a Duel in any stage of the game.
Legion Commander
* Press The Attack can save her allies dispels the stun from Shackleshot.
* Duel can lock down Windranger before she can escape with Windrun.
* Legion Commander tends to go for Blade Mail, which returns the damage she takes from Focus Fire.
Riki
* 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.
Riki
* Heroes with high base damage (Morphling, 
Tiny, Drow Ranger), heroes with mana burning abilities (Anti-Mage), and Diffusal Blade users (Juggernaut or Riki) will suffer from Reflection's illusions.
Riki
* Heroes with abilities that can lock down Terrorblade and prevent him from using Sunder: Bane, 
Batrider, 
Earthshaker, 
Elder Titan, Faceless Void, Invoker, Legion Commander, 
Mars, Primal Beast, Riki, Shadow Shaman, Silencer, 
Vengeful Spirit, Void Spirit.
Legion Commander
* Duel's long duration prevents Terrorblade from swapping his health with 
Sunder.
* Overwhelming Odds deals high damage to Terrorblade's illusions.
Riki
* Smoke Screen prevents Dark Willow from using her abilities, rendering her defenseless and unable to deal any serious damage.
* Blink Strike lets Riki jump past Bramble Maze.
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
Riki
* Heroes with silences: Puck, Doom, Riki.
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.
Legion Commander
* Duel's long duration prevents Nyx Assassin escaping from 
Vendetta. With Aghanim's Scepter, she can also bypass 
Spiked Carapace.
Legion Commander
* Heroes with long or multiple disables will prevent Legion Commander from winning Duels: Shadow Shaman, Lion
Riki
* Riki is known for being a successful support killer, something Shadow Shaman is very vulnerable to.
* Smoke Screen is particularly devastating to Shadow Shaman. With neither his various disables nor a solid health pool Shadow Shaman is usually dead. This forces Shadow Shaman to buy a 
Force Staff if he finds himself in this scenario and buy 
Sentry Wards if you have the money.
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.
Riki
* Lifestealer cannot use 
Rage, 
Infest or 
Open Wounds when affected by Smoke Cloud's silence, and 
Feast cannot heal him effectively because of the blind, leaving him very weak both offensively and defensively.
* Infest ganks are harder when the enemy team has a Riki, as there are often only four heroes on the map that you can initiate on.
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.
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
Riki
* Heroes with invisibility: (Riki, Clinkz, Nyx Assassin.
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.
Riki
* Heroes that can gank Shadow Fiend in the early game: Earth Spirit, Nyx Assassin, Riki, Spirit Breaker.
Legion Commander
* Heroes with strong area damage to destroy Phantasm illusions: Axe, Ember Spirit, Legion Commander, Phoenix
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.
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.
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
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
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
Legion Commander
* Heroes who rely on summons will see them destroyed easily by Overwhelming Odds: Lycan, Arc Warden, Warlock, Chen
Legion Commander
* Magnetic Field prevents Legion Commander from getting wins with Duel.
Additional:
* 
Magnetic Field prevents Legion Commander from easily gaining wins with Duel.
Riki
* Smoke Screen combined with Diffusal Blade leaves Arc Warden effectively useless for a while as he struggles to escape the silence with low mobility.
* With Arc Warden's low mobility, Tricks of the Trade often deal decent damage to him before he moves out of it.
Legion Commander
* Heroes who rely on summons will see them destroyed easily by Overwhelming Odds: Lycan, Arc Warden, Warlock, Chen
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.
Riki
* 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.
Riki
* Riki and 
Disruptor: Smoke Screen and 
Static Storm, respectively, can be thrown wherever Puck used Phase Shift, making Puck an easy target if it doesn't have Blink Dagger or is on cooldown. Puck is also very susceptible to Riki's high attack damage when attacking from the back. Glimpse also prevents Puck from escaping altogether.
Riki
* Because Templar Assassin does not have escape potential in lane, any support hero with roaming potential and a Dust of Appearance can be great at shutting her down early game: Earth Spirit, Spirit Breaker, Tusk, Bounty Hunter, Riki, Warlock.
Legion Commander
* 
Tethered heroes are much harder for Legion Commander to kill in Duels.
* 
Relocate can cancel Duels and save allies.
Riki
* 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, Lifestealer.
Legion Commander
* Duel is very effective against Io due to its low health and armor.
Riki
* Riki: Smoke Screen can prevent Lone Druid from using True Form and Savage Roar, additionally it cause the spirit bear to miss on attacks which reduce the chances of getting rooted from it, with diffusal Blade, he can keep Lone Druid or the Spirit Bear inside the Smoke.
Riki
* Riki with Tricks of the Trade
* Heroes that can dodge Glimpse:
* Puck with 
Phase Shift
* Riki with Tricks of the Trade
* Phantom Lancer with 
Doppelganger
* Ember Spirit with 
Sleight of Fist and 
Activate Fire Remnant
* Chaos Knight with 
Phantasm
* Naga Siren with 
Mirror Image
* Tusk with 
Snowball
* Juggernaut with Omnislash
* 
Brewmaster with 
Primal Split
* Lifestealer with Infest
* Phoenix with 
Supernova
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 make him particularly vulnerable to Legion Commander's high physical damage.
Riki
* Frail heroes who lacks mobility: Crystal Maiden, Enigma, 
Dark Willow, Vengeful Spirit.
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.
Riki
* Riki can potentially catch an Enigma out of position and prevent him from properly blinking and initiating, thanks to Cloak and Dagger.
* Before Enigma gets his Black King Bar, Smoke Screen can be used to cancel Black Hole. After Enigma gets Black King Bar, Riki can also cancel Black Hole with Abyssal Blade, which is a common item built on him.
* Tricks of the Trade renders Riki hidden and invulnerable, which in combination with Abyssal Blade allows Riki to cancel Black Hole with little to no worries of getting caught in it.
* Enigma's fragility during all stages of the game makes him extremely prone to Riki's ganking.
Riki
* With Aghanim's Scepter, Broodmother will gain access to 
Spinner's Snare, which will allow her to create invisible lines on her webs from 
Spin Web that will root, deal damage over time, and reveal enemy heroes if they unwittingly step on them. This allows Broodmother to keep her allies alerted on heroes who rely on invisibility-themed and movement-themed abilities and items to surprise enemy heroes and disrupt ganking attempts of enemy heroes: Phantom Assassin, Nyx Assassin, Mirana, Bounty Hunter, 
Templar Assassin, Riki, Spirit Breaker, Anti-Mage, Tusk, Ursa, Nature's Prophet, Enigma, Void Spirit, Magnus etc.
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.
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
Riki
* Riki can get on top of Ancient Apparition very easily with Blink Strike. This can also double as a way to dodge Ice Blast, along with Tricks of the Trade.
* Ancient Apparition will frequently resort to casting Ice Blast right before dying. Smoke Screen can be used to prevent this, stopping Ancient Apparition from having any impact.
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".
Riki
* Riki is a natural Diffusal Blade carrier, and it doesn't help that he's easily capable of sneaking up on Wraith King due to Cloak and Dagger.
* Riki can use Smoke Screen on top of Wraith King as he is reincarnating, making him a sitting duck for his second life. In addition, the blind prevents Wraith King from landing critical hits from Mortal Strike.
* Wraithfire Blast is quite predictable, and if Riki can react fast, he will disjoint it with Tricks of the Trade. There is also a chance he will become invisible again as the projectile travels, disjointing it.
Legion Commander
* Invoker's spells will disable and destroy Legion Commander while she's locked in a Duel.
Riki
* Heroes with silence: 
Death Prophet, Riki, Drow Ranger.
Legion Commander
* Heroes with long lockdowns: Shadow Shaman, Legion Commander.
Riki
* Techies is very good against roaming supports and gankers such as Bounty Hunter, Riki, Weaver, Earthshaker, Nyx Assassin, etc. that are constantly moving around the map.
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
Legion Commander
* 
Untouchable makes Enchantress one of the hardest heroes for Legion Commander to Duel against, as her attack speed will be significantly slowed for the duration, even with any form of spell immunity.
* Meanwhile, when Enchantress is not a target, Enchantress can use both 
Impetus and 
Enchant on Legion Commander to help her ally win the Duel.
Riki
* Riki usually buys Diffusal Blade to initiate, which renders Enchantress' movement speed useless, and is usually followed with Smoke Screen.
* Riki can effectively hit Enchantress by Tricks of the Trade alongside with Diffusal Blade and Smoke Screen's initiation. For a hero like Enchantress, 3 to 4 hits from Riki is a big deal, unless Enchantress built Force Staff earlier.
Riki
* Viper's 
Nethertoxin disables Cloak and Dagger, negating Riki's invisibility and much of his damage. It also makes him more vulnerable to magic damage, which does not go well with Riki's low health pool. With the talent applied, he can't even blink to safety or hide with Tricks of the Trade.
* 
Corrosive Skin makes it hard for Riki to chase Viper and attack him due to the attack speed slow.
* 
Viper Strike stays on Riki even after he goes invisible.
* 
Poison Attack makes it risky for Riki to get last hits and can make the laning phase difficult for him.
Legion Commander
* Viper's frailty and low mobility make 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.
Riki
* Heroes who rely on their target to run away: Riki, Bounty Hunter.
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.
Riki
* Blink Strike gives bonus backstab damage and can bypass Bulwark. Defensively, it could be used to teleport away from Mars, especially while inside Arena of Blood.
* Smoke Screen can interrupt Mars' skill combos, especially when cast inside Arena of Blood.
* Tricks of the Trade can be used to evade Mars' skills, which have a slight delay to them. It could also be used to buy himself time while trapped inside of Arena of Blood.
Additional:
* Bulwark is generally irrelevant against Riki as he primarily deals bonus damage from behind.
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.
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.
Riki
* Cloak and Dagger makes Sven unable to detect where Riki is until he shows or his team provides detection.
* Smoke Screen will make Sven miss attacks before he has his Black King Bar.
Legion Commander
* 
Paralyzing Cask can save ally from Legion Commander Duel's until she purchases 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.
Riki
* Without Dust of Appearance or Sentry Wards, Riki is able to silence Witch Doctor with Smoke Screen, and is likely to build a Diffusal Blade, leaving Witch Doctor without mana to cast Voodoo Restoration, as well as Skull Basher to interrupt Death Ward.
Legion Commander
* 
Mystic Flare can easily burst down Legion Commander while she is Dueling.
Riki
* Due to his low health and armor, Riki can easily kill Skywrath Mage.
* Smoke Screen prevents Skywrath from using all of his abilities, as he does not tend to buy Black King Bar.
* However, Skywrath Mage can easily kill Riki if he manages to root Riki with Rod of Atos or Gleipnir, followed by Dust of Appearance, Ancient Seal and Mystic Flare.
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.
Riki
* 
Spectral Dagger follows Riki even after he goes invisible and stays on him through Tricks of the Trade, revealing his location.
* 
Desolate grants Spectre the ability to damage Riki with right clicks regardless of Smoke Screen's blind.
* Riki relies on his high damage to kill is opponents, which is countered by 
Dispersion.
* 
Haunt can find Riki globally at any time, negating much of his ganking potential.
Riki
* Riki's Smoke Screen can make it hard for Spectre to escape or burst down Riki with auto attacks.
* Riki can build Aghanim's Scepter and jump inside an allied carry or offlane tank with Tricks of the Trade to do a lot of damage to Spectre while completely avoiding Dispersion.
* Riki is great at destroying supports which are often needed to keep Spectre safe until she comes online. He can take them down quickly in team fights, which will leave Spectre alone against your whole team, a fight that she will most likely not win.
* While on Tricks of the Trade, Riki does not take damage from Dispersion.
Riki
* Quill Spray will hit Riki even when he is invisible.
* Cloak and Dagger's bonus backstab damage is rendered irrelevant against Bristleback.
* Smoke Screen does not stop Bristleback's passive from activating.
* Due to Bristleback's natural tankiness, he is an ideal 
Gem of True Sight carrier, directly countering Riki's invisibility.
Additional:
* The bonus Backstab damage from Cloak and Dagger is rendered irrelevant with 
Bristleback and hurts Riki more than him because of the passive Quill Spray.
* Riki can still get damaged by Bristleback's 
Quill Spray while invisible, and it can be hard to deal with in lane.
* Bristleback is not too bothered by Smoke Screen. Though he cannot use Quill Spray manually inside it, it still procs passively when he takes damage from the back. The movement speed from 
Warpath allows him to get out of the area easily.
* Due to Bristleback's natural tankiness, he is an ideal Gem of True Sight carrier.
* Riki rarely buys Silver Edge to break Bristleback's passive because the invisibility aspect of it is redundant.
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.
Riki
* Invisibility reliant heroes: Heroes with invisibility abilities or those that have invested into invisibility items are hindered by Bounty Hunter's Track. Few examples of such heroes are:Clinkz, Riki, Treant Protector, etc.
Additional:
* 
Track reveals Riki while invisible and gives him a hard time, as it prevents much of his ganking capabilities. This can force Riki to buy Manta Style to dispel it.
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.
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
* With Smoke Screen, Riki will silence and catch Medusa in a surprise with high miss chance flushing her from positions easily in team fights.
* He can deal a huge amount of damage through Cloak and Dagger, even through Mana Shield.
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
Riki
* Riki can detect early Roshan attempts because of Cloak and Dagger if he frequently checks the Pit.
* Ursa cannot Enrage when in Smoke Screen (Black King Bar will help though).
* Even if Ursa gets vision over him, Riki can Blink Strike away or use Tricks of the Trade after Ursa's initiation to avoid all Fury Swipes damage until 
Earthshock's slow is gone.
Additional:
* Riki can detect early Roshan attempts because of Cloak and Dagger if he frequently checks the Pit.
* Ursa cannot Enrage when caught in Smoke Screen and will miss his attacks (although Black King Bar will help with this issue).
* Even if Ursa gets vision over him and initiates with Earthshock, Riki can Blink Strike away or use Tricks of the Trade after Ursa's initiation to avoid Fury Swipes' damage until Earthshock's slow is gone.
Riki
*
Corrosive Haze works much like 
Track, giving the enemy team vision over Riki. While it doesn't give a movement speed or gold bonus, it instead can melt Riki's armor and Slardar can use 
Guardian Sprint to catch up to him.
Aghanim's Shard, causes 
Slithereen Crush to apply Corrosive Haze even if Slardar does not have vision over him.
* Slardar's
Additional:
* Corrosive Haze makes Riki completely vulnerable to Slardar and his allies, as Riki has no easy way of dispelling it.
* Slardar's physical damage with Slithereen Crush and Bash of the Deep amplified by Corrosive Haze can easily kill Riki.
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.