* Since Windranger is bad against magical damage, heroes with continuous magical damage or magical nukes can blast her: Zeus, Tinker, Leshrac, Viper, Skywrath Mage, Lion, Lina, Venomancer.

* Heroes with Attack speed decreasing skills: Jakiro, Viper Lich

* Heroes whose core item builds includes Monkey King Bar: Faceless Void, Windranger, Weaver, Juggernaut.

* Juggernaut's Healing Ward keeps his team healthy even when pushing against Keeper of the Light's Illuminate.
* Blade Fury can dispel Blinding Light, as well as dodge an incoming Illuminate. Juggernaut can attack towers during Blade Fury, so he can dodge an Illuminate without having to stop pushing.
* Should Keeper of the Light obtain Will-o-Wisp through purchasing an Aghanim's Scepter, Juggernaut can make quick work of Ignis Fatuus without being interrupted by its pull.
* Keeper of the Light has low health, low armor, and no natural defense against Blade Fury.
Additional:
* Blade Fury allows him to be immune to all of Ezalor's abilities.
* Healing Ward heals his entire team, mitigating Ezalor's weak magical burst damage.

* Blade Fury offers good AoE damage to clear illusions and can hurt the real Naga Siren as well if she chooses to blend in the illusions. Diffusal Blade does nothing to Juggernaut either when he uses Blade Fury.
* Aghanim's Shard upgraded Blade Fury along with Lv 20 DPS talent will shred all illusions almost instantly, especially when combined with Mjollnir, a common item for Juggernaut.

* Heroes who can harass Omniknight out of lane will keep him weak in the mid game: Viper, Venomancer, Clinkz.

* Heroes with built-in spell immunity can become immune to all of Outworld Destroyer's spells: Lifestealer's Rage and Juggernaut's Blade Fury.

* Melee heroes with low mobility can be kited and killed by Viper: Treant Protector, Kunkka, Alchemist, Troll Warlord, Wraith King, Tiny, Sven.

* Viper's skill set makes him an effective early game ganker against Anti-Mage before he is sufficiently farmed.
* Viper's Corrosive Skin and low mana pool causes him to take little damage from Mana Void.
* Nethertoxin disables Mana Break and Counterspell, weakening both his offense and defense.

* Juggernaut can trigger Proximity Mines while in Blade Fury, and can walk away from a initiation with Blast Off if Blade Fury is activated before the silence.
* Juggernaut ignores Reactive Tazer when he uses Omnislash, whether Techies used it to protect an ally or themselves.

* Corrosive Skin will protect Viper from Techies' magical damage.
* Even though Reactive Tazer will disarm Viper if he attacks Techies with Poison Attack, he does lots of damage with his other abilities that can still kill Techies.

* Blade Fury's damage over time dispels Refraction almost instantly.
* Juggernaut's high armor allows him to survive for long enough to remove Refraction and threaten her with Omnislash as long as he or his team carries detection.
* Templar Assassin's short attack range makes it difficult for her to target a well-placed Healing Ward. She cannot splash onto it with Psi Blades.

* The damage over time from Viper's Poison Attack and Viper Strike rapidly wear down Refraction charges, allowing Templar Assassin to be damaged. Additionally, Corrosive Skin causes her attacks to apply damage overtime on her as well.
* Nethertoxin is a big threat to Templar Assassin. Her initially low range making it very hard to deal against Nethertoxin in the laning phase. At any stage of the game, a Nethertoxin can always force her to undo her Meld.
Additional:
* All of Viper's abilities quickly burn through Refraction charges.
* Templar Assassin's short range, aside from Psi Blades' spill damage, makes her vulnerable to Poison Attack harassment.
* Templar Assassin usually buys health and armor items for damage. Outside of Black King Bar, Viper will almost always be able to kill her when Refraction is down.

* None of Zeus's abilities can damage a Juggernaut in Blade Fury.
* Zeus's short attack range makes it difficult for him to target a well-placed Healing Ward. His frequent use of Arc Lightning will have almost no effect on allies being healed by Juggernaut.
* Zeus has no way to defend himself, even if Juggernaut cannot use Blade Fury. He can be easily taken out if cornered, sometimes even without Omnislash.
Additional:
* Blade Fury negates all magical damage from Zeus.
* Omnislash can easily take down Zeus. However, be aware that most players will get a Eul's Scepter of Divinity or a Ghost Scepter against Juggernaut.

* Corrosive Skin severely reduces Zeus's damage output throughout the game.
* During the laning stage, Viper can abuse Zeus' reliance on spells by hugging the creep wave. Zeus will take constant damage over time from Corrosive Skin unless he drives Viper from the lane or returns to farming in his absence.
* Prior to buying Blink Dagger or Force Staff, Zeus is fragile and possesses low mobility. Any of Viper's numerous slows can set up an easy kill.
Additional:
* Corrosive Skin counters Zeus in lane by canceling the effects of Clarity as Zeus relies on Arc Lightning to farm and secure last hits.
* Corrosive Skin also increases Viper's magic resistance to shrug off Zeus's magical nukes.
* Nethertoxin breaks Static Field.
* Due to Zeus' poor mobility, Viper Strike will cripple Zeus and will allow Viper and his teammates to land a lot of attacks.

* Juggernaut's Healing Ward can help save allied supports when Spectre attempts a Haunt kill.
* Juggernaut has a stronger push potential than Spectre, enabling him to end the game early before Spectre can come online.
* Spectre is often paired with two supports that are often weak against Juggernaut.
* Juggernaut also tends to build a Manta Style, which can prevent Desolate from taking effect.
* Juggernaut is invulnerable against Dispersion while using Omnislash.

* Nethertoxin disable passives, negating Spectre's damage and survivability by removing both Dispersion and Desolate.
* Due to Haunt and Radiance's burn, Spectre is heavily susceptible to being persistently slowed and damaged by Corrosive Skin without even directly attacking Viper.
* Poison Attack and Viper Strike further slow Spectre's movement speed to a crawl, while his improved magic resistance means he can easily shrug off Radiance's burn.
Additional:
* Viper Strike can disable Desolate and Dispersion, leaving Spectre with far less damage output and damage mitigation in engagements.
* Spectre is one of the weakest heroes at early levels. Viper can stifle her farm with early fights before Spectre purchases any major items.

* Blade Fury protects Juggernaut from all of Tiny's magic burst damage.

* Tiny has low movement speed and attack speed, making him vulnerable to Viper's slows.
* Corrosive Skin provides magic resistance to lower Tiny's magic burst damage.

* Blade Fury makes Juggernaut immune to the damage from Life Break and Burning Spears.
* It can be instantly activated the second Juggernaut sees Huskar flying towards him with Life Break, blocking all damage.
* Healing Ward effectively negates any damage-over-time from Burning Spears.
* Huskar has no defense against Omnislash and takes heavy damage due to his low armor.

* His Poison Attack is very useful against Huskar, since he tends to stay at low health.
* Nethertoxin disables passive skills like Berserker's Blood.
* It is dangerous for Huskar to jump on Viper because Corrosive Skin and Viper Strike with the slowdown of movement and attack speed which usually will be deadly for Huskar.
Additional:
* Viper Strike can disable Berserker's Blood, which Huskar relies upon for attack speed and healing.
* The damage from Burning Spear and Life Break is largely absorbed by Corrosive Skin. It also will return some damage, making it risky to use Burning Spears in the laning stage.
* Because Huskar wants to be on low health for Berserker's Blood, he is particularly vulnerable to Poison Attack.

* Blade Fury makes Juggernaut immune to all Nyx's abilities, except Vendetta.
* Omnislash. and Swiftslash can burst Nyx down, ignoring Spiked Carapace. However, Vendetta can be used to escape, canceling Omnislash/Swiftslash.
Additional:
* Juggernaut's entire skillset greatly counters Nyx Assassin's Spiked Carapace, his most important ability.
* Blade Fury allows Juggernaut to freely attack Nyx Assassin, and deal heavy damage to Nyx Assassin. Nyx Assassin cannot counter Blade Fury with Spiked Carapace because Blade Fury gives Juggernaut spell immunity. And besides Vendetta, Nyx Assassin has no other way of dealing damage to Juggernaut while he is spell immune.
* Healing Ward allows Juggernaut to recover himself and his allies from Nyx Assassin's damage output.
* Omnislash and Swiftslash from Aghanim's Scepter can quickly finish off Nyx Assassin. And just like Blade Fury, Nyx Assassin cannot counter neither Omnislash and Swiftslash from Aghanim's Scepter with Spiked Carapace because both abilities render Juggernaut invulnerable. And if Nyx Assassin has no Vendetta available to use for escaping, both abilities will kill him very quickly before he can do anything.
* Overall, any attempt for Nyx Assassin to gank and kill Juggernaut will hurt Nyx Assassin more than Juggernaut.

* Corrosive Skin minimizes the damage from Impale and Mind Flare, and anything else Nyx Assassin tries to throw at Viper.
* Nyx Assassin cannot survive several poison damage-over-time output from Poison Attack, Nethertoxin, Corrosive Skin and Viper Strike, not even while he has Spiked Carapace active. And to make things worse, Nyx Assassin is not a common Silver Edge wielder to counter this problem at all.
Additional:
* Corrosive Skin minimizes the damage from Impale and Mind Flare, and anything else Nyx Assassin tries to throw at Viper.
* Nyx Assassin cannot survive several poison damage-over-time output from Poison Attack, Nethertoxin, Corrosive Skin and Viper Strike, not even while he has Spiked Carapace active. And to make things worse, Nyx Assassin is not a common Silver Edge wielder to counter this problem at all.

* Kraken Shell provides no protection against Omnislash or Swiftslash.
* If timed correctly, Omnislash, Swiftslash and Blade Fury are all capable of dodging Ravage, giving Juggernaut several tools to render your strongest ability moot.
* Blade Fury is an effective way to harass Tidehunter in the laning stage as Tidehunter has no means of getting Juggernaut away from him. Healing Ward also greatly minimizes Tidehunter's ability to harass Juggernaut.
* Blade Dance minimizes the effectiveness of Anchor Smash's damage reduction.

* Viper STrike cancels out Kraken Shell and stops the hard dispel from passively activating, preventing Tidehunter from functioning as a frontline tank.
* Anchor Smash is mostly irrelevant against a ranged hero like Viper.
* Tidehunter relies on the threat of Ravage, which has an obscenely long cooldown. Viper can exploit the downtime with his short cooldowns.

* Juggernaut's high attack speed lets him destroy a Supernova easily. He can even attack a Supernova during Blade Fury with his regular attacks.
* Blade Fury protects Juggernaut from all of Phoenix's spells (except Supernova, which pierces spell immunity).
* Blade Fury can also dispel the attack speed slow from Fire Spirits and the movement speed slow from Icarus Dive.
* Phoenix's Icarus Dive will not protect it from Omnislash unless it dives into creeps, and Phoenix's low armor makes for an easy kill.

* Corrosive Skin gives Viper additional resistance to Phoenix's magical damage, and since they deal damage over time, Phoenix would be constantly afflicted by his passive's own debuff, making him not an ideal target for Phoenix's harassment. Phoenix's abilities also constantly drain its own health away, becoming more vulnerable to Poison Attack.

* Blade Fury allows Juggernaut to simply move out of Kinetic Field and to dodge Glimpse.

* Corrosive Skin minimizes the damage Viper takes from all of Disruptor's skills.

* Blade Fury dispels the slow from Enchant, and can burst Enchantress down during the laning stage.
* Omnislash and Swiftslash's physical damage burst ignore untouchable.
* Silver Edge is a common item for Juggernaut for dealing with Untouchable.
Additional:
* Blade Fury dispels the slow from Enchant, spell immunity and used to burst her down during the early laning stage.
* Omnislash and Swiftslash's physical damage burst ignore Untouchable.
* Silver Edge is an ideal item for Juggernaut to deal with Untouchable, making her vulnerable to melee attacks.

* Heroes with break can disable Untouchable for a while: Doom and Shadow Demon (via Aghanim's Scepter), Viper, Shadow Shaman with Hex Breaks talent.

* 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.

* Corrosive Skin minimizes the damage Viper takes from all of Ancient Apparition's abilities.
* Ancient Apparition's slow movement speed, squishy nature, and lack of escape abilities can easily be taken advantage of through Poison Attack and Viper Strike.

* Blade Fury negates Kunkka's X Marks the Spot.
* Kunkka has no way to dodge Omnislash.
* Kunkka has no way to hit Healing Ward directly in battle, and it mitigates Ghostship and Tidebringer's damage.

* Melee heroes with low mobility can be kited and killed by Viper: Treant Protector, Kunkka, Alchemist, Troll Warlord, Wraith King, Tiny, Sven.

* Heroes with spell immunity unless Lina chooses to play Carry role like Lifestealer with Rage and Juggernaut with Blade Fury.

* Viper Strike prevents buildup of Fiery Soul stacks.
* Corrosive Skin provides magic resistance against Lina's spells. However, Lina can counter this with Silver Edge, a common item on Lina.
* Poison Attack and Viper Strike can burn away Lina's small health pool.

* Juggernaut with Blade Fury
* 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.

* Viper's poison abilities can slow Bounty Hunter's movement speed and allows to chase him with True Sight items.
* Nethertoxin can break Jinada, and the silence from level 25 prevents Bounty Hunter from using all of his spells.

* Blade Fury blocks the damage done by Death Pulse and Reaper's Scythe. Additionally, Ghost Shroud decreases Necrophos's magic resistance, making him take more damage from Blade Fury.

* Viper does large amounts of magic damage over time, meaning that if a Necrophos uses Ghost Shroud, Viper's abilities will greatly reduce Necrophos survivability, and may actually kill him.
* By the same token, Viper can use his Viper Strike on Necrophos if he attempts to heal himself with Ghost Shroud, and depending on any other effects Necrophos may have from him, (IE:Poison Attack,Corrosive Skin), Viper can often kill Necrophos while he is in his Ghost Shroud.
* Viper's Corrosive Skin helps him take reduced damage from all of Necrophos spells that deal magical damage, which is his only source of damage.
Additional:
* Viper Strike prevents Heartstopper Aura from dealing damage or healing Necrophos.
* Viper's magic damage is amplified whenever Ghost Shroud is used.
* Corrosive Skin makes Viper tankier against Death Pulse and Reaper's Scythe.

* Juggernaut and Lifestealer have abilities (Blade Fury and Rage respectively) that prevent Crystal Maiden from using her spells on them in the early game, before Black King Bar and other magical reduction is even an issue.

* Heroes who can easily harass Crystal Maiden out of lane in the early game (Clinkz, Viper) can prevent Crystal Maiden from being able to level effectively, and can ultimately slow down her level 6, 12, and 18 to a point where enemy carries already have items to address her ultimate.

* Blade Fury makes Juggernaut immune against all of Snapfire's spells and allows him to get closer.
* A well-timed Omnislash allows Juggernaut to dodge Snapfire's spells, and she has no way to deal with it.

* Blade Fury grants spell immunity and also allows him to deal massive magical damage, both of which are Muerta's general counters.
* However, Juggernaut has no way of hurting Muerta through Pierce the Veil outside of Blade Fury, Juggernaut's only source of dealing magical damage. And unlike other abilities and items that turn the user ethereal, Pierce the Veil cannot be dispelled at all, making Nullifier useless for Juggernaut. This forces Juggernaut to buy Revenant's Brooch.

* Nethertoxin prevents the buildup of Jingu Mastery stacks.
* Viper's poison magical damage-over-time stops Monkey King from using Tree Dance. It also ignores the extra armor bestowed by Wukong's Command.
Additional:
* Viper STrike prevents the buildup of Jingu Mastery stacks.
* Monkey King's high base movement speed is of little worth against the array of slows Viper possesses.
* All of Viper's magical damage over time stops Monkey King from using Tree Dance. It also ignores the extra armor bestowed by Wukong's Command.

* The slow applied from Corrosive Skin offsets the movement speed bonus granted by Scorched Earth and the tick-based damage from Infernal Blade and Doom will continually slow Doom down. This allows Viper, much like Sniper, to 'kite' Doom and keep him at a safe distance between the two. Additionally, Corrosive Skin applies an attack-speed slow which is fairly crippling to a hero such as Doom that, naturally, has a high base attack-time, poor agility gain and builds little attack-speed items.
* Since Doom does not disable auto-cast abilities, Viper's Poison Attack will continue to work. Doom may find it hard to close the distance between himself and Viper, and thusly difficult to effectively lockdown and continually deal damage through his abilities.

* Corrosive Skin means Viper can often outlast Venomancer in a battle of attrition.
* Venomancer has no mobility without items, which makes him vulnerable to constant slows.

* Nethertoxin disables Bristleback's passive.
* Viper Strike and Poison Attack slow down Bristleback's movement speed, making him unable to get out from Nethertoxin.
Additional:
* Viper Strike can disable Bristleback and prevents Warpath from building stacks. Besides losing his defensive passive, Bristleback also loses his ability to build up damage over lengthy battles.
* Viper can perpetually kite Bristleback with Poison Attack and Viper Strike.

* Blade Fury, similar to Rage, grants immunity to Invoker's spells and can dispel some debuffs as well.
* Omnislash renders Juggernaut invulnerable to Invoker's spells and can easily take Invoker down.
Additional:
* Juggernaut's instant spell immunity from Blade Fury. helps him dodge Invoker's combos. He can dispel the disables from Cold Snap and Deafening Blast and dodge the damage from Chaos Meteor, as well as walk through Ice Wall.
* Juggernaut's high DPS allows him to kill split pushing Forge Spirit(s) effortlessly, and his high armor prevents them from being a threat to him.
* However, Invoker can hit Juggernaut with Sun Strike through Blade Fury, making the Tornado and Sun Strike combo a threat if he does not dodge Tornado.

* Corrosive Skin makes Viper receive less damage from Invoker's spells
* Viper can harass Invoker with his Poison Attack in the early game.
* Viper Strike and Poison Attack can kill Invoker easily if Ghost Walk is on cooldown.

* Blade Fury and Omnislash allows Juggernaut to avoid Gyrocopter's area attacks entirely.

* Heroes with spell immunity or pseudo-blinks which provide invulnerability: Lifestealer, Juggernaut, Omniknight, Huskar, and Tusk have spells which allow them to easily escape Dream Coil.

* Viper wins on the central line of Puck, because he has a huge damage from the Poison Attack ability, which Puck is not able to constantly avoid using Phase Shift, which will give Viper an advantage in the possible damage inflicted on each other
* Puck takes more damage than it does due to the passive Corrosive Skin ability of the Viper, which makes it unprofitable for the Puck to fight against the Viper at an early stage of the game, when the Puck has a very small pool of health.
Additional:
* Viper wins on the central line of Puck, because he has a huge damage from the Poison Attack ability, which Puck is not able to constantly avoid using Phase Shift, which will give Viper an advantage in the possible damage inflicted on each other
* Puck takes more damage than it does due to the passive Corrosive Skin ability of the Viper, which makes it unprofitable for the Puck to fight against the Viper at an early stage of the game, when the Puck has a very small pool of health

* Viper Strike prevents Timbersaw from gaining stacks on Reactive Armor.

* Nethertoxin both Necromastery and Presence of the Dark Lord, reducing his damage massively.
* Corrosive Skin gives Viper bonus Magic Resistance against Shadowraze and Requiem of Souls.
* Viper can easily take advantage of Shadow Fiend's lack of escape and mobility spells with Viper Strike breaks and Poison Attack. Poison Attack also serves as a great way to harass Shadow Fiend.

* Nethertoxin disables Dawnbreaker's Luminosity. Since she's a melee hero, she needs to close gap to attack and Nethertoxin will be bad for her since she cannot heal.
* Viper Strike and Poison Attack will severely slow her down and combined with Nethertoxin, it will be her death sentence (unless her Celestial Hammer or Solar Guardian are off cooldown). Besides that, chasing her down will be easy due to the slow.

* Blade Fury dispels most of Dark Willow's abilities, allowing Juggernaut to pass through Bramble Maze and cancel out Cursed Crown before the stun occurs.
* However, Dark Willow can tank Omnislash with Shadow Realm. As she is a valid target, but invulnerable to right clicks.
Additional:
* None of Dark Willow's spells pierce Spell Immunity, making Blade Fury a good counter against her. Additionally, it dispels Cursed Crown and Bramble Maze.
* Dark Willow is generally fragile, which results in Omnislash being devastating against her.
* However, if Shadow Realm is activated during Omnislash, then the attack damage is negated (though Omnislash can still jump to other enemies).

* Poison Attack makes it hard for Void Spirit to lane against him.
* Corrosive Skin reduces the magical damage from Void Spirit's spells.

* Viper Strike breaks Multicast.
* Corrosive Skin minimizes the damage from Ignite and Fireblast.

* Poison Attack and Viper Strike allowing to kite and slow Earthshaker significally, putting Blink Dagger on cooldown and preventing him from initiating or re-initiating.
* Nethertoxin breaks Aftershock. The silence from Level 25 talent also prevents Earthshaker from initiating or re-initiating.
Additional:
* Being a melee hero, Earthshaker's movement is liable to suppression by Poison Attack and Viper Strike.
* Earthshaker's kit, with the exception of Enchant Totem, deals magic damage. Corrosive Skin effectively blunts his killing potential with a standard Blink combo among other things.
* Viper Strike can disable Aftershock, which removes the stun and bonus damage from Enchant Totem and Echo Slam.

* Juggernaut is invulnerable while using Omnislash, meaning that neither Blade Mail or Power Cogs will save Clockwerk, this is especially common during the early laning phase.
* Blade Fury will also ignore any damage dealt by Battery Assault, as well as dealing heavy damage. As long as Juggernaut has mana to cast it.
* Overall, any attempt for Clockwerk to trap Juggernaut with Power Cogs will hurt him a lot more than the other way around.

* Viper Strike can disable Gravekeeper's Cloak, Visage's primary defense mechanism.
* Viper can ignore Grave Chill's attack speed slow with his magic damage output.
Additional:
* Since Visage is a slow hero, Viper can easily kite him with Poison Attack and Viper Strike while successfully chipping away at Gravekeeper's Cloak.
* Nethertoxin removes all layers of Gravekeeper's Cloak, leaving Visage exposed.
* Corrosive Skin makes Viper highly resistant to Soul Assumption.

* Hand of God has a long cooldown, so damage over time spells can be hazardous for Chen, forcing him to use it prematurely: Jakiro, Venomancer, Viper, Dazzle, Phoenix.

* Any hero who can survive Magnus's initiations and manfight him: Huskar, Faceless Void, Weaver, Abaddon, Troll Warlord, Alchemist, Dragon Knight, Night Stalker, Viper.

Additional:
* Most of Magnus's abilities except Empower will trigger damage through Corrosive Skin.
* Poison Attack and Viper Strike can slow Magnus during Skewer, as well as putting his Blink Dagger on cooldown, preventing him from initiating or re-initiating.

* Illusion heroes like the aforementioned Phantom Lancer or Naga Siren, or heroes that tend to buy Manta Style, like Luna or Juggernaut, will give Slardar a hard time, as his damage is single-targeted.

* 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.

* Heroes with good mobility to avoid Jakiro's abilities and with good chase to punish Jakiro from pushing a tower: Bloodseeker, Ember Spirit, Juggernaut, Phantom Assassin, Weaver.

* Heroes that can slow Charge of Darkness by a huge amount: Venomancer, Viper, Dazzle, Arc Warden, Lion, Huskar, Shadow Shaman, Visage, Undying, Jakiro.

* Heroes with spell immunity: Juggernaut, Pangolier, Huskar.

* Heroes that can apply early pressure before Phantom Assassin has farm are massive threats: Axe, Viper, Meepo, Jakiro, Pugna, Slark, Venomancer etc.

* Viper can bully Alchemist out of mid lane quite easily, forcing him to either retreat into jungle, or stay harassed in lane, and get very few last hits. Vipers break also completely disables Greevil's greed which prevents Alchemist to earn his amazing amounts of money.

* Skywrath's pitiful defences also make him easy meat to heroes with high burst like Juggernaut, Lion, or Phantom Assassin, the latter occasionally downing a support Skywrath in a single Stifling Dagger.

* Wraithfire Blast is quite predictable, and players with good reflexes will disjoint it with Blade Fury.
* Omnislash with Diffusal Blade & Aghanim's Scepter can prevent Wraith King from reincarnating unless he has his Aghanim's Shard that removes the mana cost from Reincarnation.

* Melee heroes with low mobility can be kited and killed by Viper: Treant Protector, Kunkka, Alchemist, Troll Warlord, Wraith King, Tiny, Sven.

* Heroes with stronger lane presence that can threaten to kill him: Batrider, Juggernaut, Ursa, Monkey King, Razor.

* Heroes that build Diffusal Blade or can fit it well into their item build will also make Medusa much less tanky: Riki, Naga Siren, Terrorblade, Juggernaut, Spectre, Slark.

* In the early game, a Dragon Knight without Black King Bar is basically defenseless against Viper.
* Viper can harass Dragon Knight at any time with his Poison Attack and Nethertoxin.
* Corrosive Skin reduces damage from Dragon Fire and inflicts damage to him.
* Viper Strike disables Dragon Blood, negating his main survivability.
* Viper Strike and Poison Attack can severely slow him down even with his Elder Dragon Form.
Additional:
* Dragon Knight is easily harassed by Poison Attack after the laning stage ends.
* Corrosive Skin protects Viper from Breathe Fire and returns damage.
* Viper Strike can disable Dragon Blood, Dragon's Knight main source of armor and health regeneration.
* Between Poison Attack and Viper Strike, Viper can keep Dragon Knight permanently slowed even in Elder Dragon Form.

* 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.

* Viper's Poison Attack and Viper Strike that can slow Razor, and is one of the few heroes that can keep him immobile.
* Altogether, Viper's skills reduce Razor's attack speed, heavily reducing the benefit of the damage drain from Static Link.
Additional:
* Storm Surge is counteracted by Viper Strike, leaving Razor without his extra movement speed.
* Static Link's damage drain doesn't bother Viper a lot as most of his early to mid game damage is magical.

* Viper Strike prevents the lifesteal from Ransack.
* Meepo and his clones have a lack of magic resistance, so they're vulnerable to Poison Attack & Viper Strike directed onto one clone.

* Nethertoxin disables Vengeance Aura.
* Vengeful Spirit has no mobility spells aside from Nether Swap, which Viper can take advantage of with his slows.
* Viper can easily bully Vengeful Spirit out of a lane with Poison Attack.
Additional:
* Viper Strike can disable the attack damage bonus from Vengeance Aura and the components of Nether Swap.
* Both Magic Missile and Wave of Terror are counteracted by Corrosive Skin, making Vengeful Spirit's fighting harder against Viper.

* Poison Attack and Viper Strike slows Axe significantly, and puts his Blink Dagger on cooldown, preventing him from initiating. Viper Strike can also break from Counter Helix.
Additional:
* Viper Strike prevents Counter Helix from triggering, which significantly lowers Axe's damage output in the early to mid game.
* Viper's various slows and damage over time prevents Axe from initiating as well as putting his Blink Dagger on cooldown.

* Because Poison Attack has almost no cooldown, Aphotic Shield is ineffective as a hard dispel.
* Viper Strike can prevent Borrowed Time from activating passively and block Curse of Avernus.
Additional:
* Because Poison Attack has almost no cooldown, Aphotic Shield is ineffective as a hard dispel.
* Viper Strike can prevent Borrowed Time from activating passively and block Curse of Avernus.

* Nethertoxin breaks the damage block from Bulwark.
* Poison Attack and Viper Strike's slows make it difficult for Mars to contribute to fights due to his low mobility.
Additional:
* Viper Strike can disable Bulwark entirely, making Mars far less tanky. Using Nethertoxin inside Arena of Blood may discourage enemies from following up with Mars's initiation.
* Rod of Atos is currently common on Viper and keeps Mars in position long enough to be killed.
* However, Viper is not very tanky earlier in the game, so positioning against Mars is important for Viper since a well-timed Spear of Mars can be the end of Viper.

* Viper Strike breaks Sniper's passives.
* Corrosive Skin allows Viper to deal more damage to Sniper than Sniper deals to him when laning, especially by briefly stepping into Shrapnel.
* Nethertoxin together with Poison Attack can slow Sniper and tears through his low health and mobility.

* Because of her low range, Luna cannot easily destroy Healing Ward.
* Both Blade Fury and Omnislash are direct counters to Eclipse, offering Juggernaut spell immunity and invulnerabilty. Therefore, Luna will need assistance in taking down Juggernaut as going solo will not be successful.
* For the same reasons, Juggernaut makes a very powerful ally for Luna when they are in the same team.

* Heroes with Break abilities will prevent Slark from regenerating and gaining Essence Shift stacks: Viper, Shadow Demon, etc.

Additional:
* Viper Strike can disable Essence Shift and the regeneration aspect of Shadow Dance.
* Dark Pact doesn't mean a lot against Viper's ubiquitous slows.
* Viper becomes a relevant presence in team fights before Slark can procure his standard items (e.g. Shadow Blade).

* Melee heroes with low mobility can be kited and killed by Viper: Treant Protector, Kunkka, Alchemist, Troll Warlord, Wraith King, Tiny, Sven.

* Blade Fury makes Juggernaut immune to Elder Titan's stun, so there is a high chance he wont get caught in your ultimate although Earth Splitter pierces spell immunity.

* Heroes with spell immunity abilities won't be caught inside by Pit of Malice: Juggernaut, Lifestealer.

* Viper Strike is a strong and breaks Fury Swipes, undispellable slow, making it much easier to kite Ursa for everyone.

* Melee heroes with low mobility can be kited and killed by Viper: Treant Protector, Kunkka, Alchemist, Troll Warlord, Wraith King, Tiny, Sven.