* Berserker's Call forces Mars to face in the direction choosen.
* Counter Helix deals pure damage and can go through Bulwark.

* 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:
* Nethertoxin disables Bulwark entirely, making Mars far less tanky. Using Nethertoxin inside Arena of Blood may discourage enemies from following up with Mars' initiation.
* Rod of Atos is currently common on Viper and keeps Mars in position long enough to be killed.
* Beware that Viper is not very tanky earlier in the game, so positioning against Mars is important since a well-timed Spear of Mars can be the end of Viper.

* Berserker's Call and Counter Helix allow Axe to kill Shadow Fiend if he stands too close to a creep wave.
* Battle Hunger is very strong against Shadow Fiend in the early game because Shadow Fiend's low attack damage makes it hard for him to get last hits.
* Axe's naturally high strength and health regeneration will be enough to tank a lot of Shadow Fiend's damage in the early game.

* Nethertoxin breaks 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 and Poison Attack. Poison Attack also serves as a great way to harass Shadow Fiend.

* Culling Blade's instant kill is not prevented by Borrowed Time should Abaddon's health falls below the threshold.
Additional:
* Culling Blade ignores Borrowed Time should Abaddon's health falls under the threshold.
* Aphotic Shield does nothing against Berserkers Call and has to be used constantly to remove the very small mana cost of Battle Hunger in lane.

* Because Poison Attack has no cooldown, Aphotic Shield is ineffective as a hard dispel.
* Nethertoxin prevents Borrowed Time from activating passively and blocks Curse of Avernus

* Huskar is often played at low health to maximize the bonuses from Berserker's Blood, and also because his abilities cost health to use. This makes him especially vulnerable to Culling Blade.
* Berserker's Blood gives Huskar no protection against the pure damage of Culling Blade. Its attack speed bonus also means that Counter Helix will proc more often.
* Axe's tankiness and base health regeneration makes it hard for Huskar to take him down with Burning Spears.
Additional:
* Berserker's Call and Blade Mail can be used immediately after Huskar jumps on Axe with Life Break.
* Huskar's high attack speed procs Counter Helix repeatedly.
* Huskar's health loss from using his abilities make him a frequent target for Culling Blade.

* 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:
* Nethertoxin disables 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.

* 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.

* 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.

* Axe can Berserker's Call into a flock of Familiars, proccing Counter Helix and killing them off.
* Familiars' very fast attacks will proc Counter Helix, receiving full damage due to their low attack range.

* Nethertoxin cuts off 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.

* Heroes that can keep Monkey King stunned for a long time can pose a threat: Axe, Centaur Warrunner.

* 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:
* Nethertoxin 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.

* Axe can force Alchemist to attack him with Berserker's Call. High attack speed from Chemical Rage will cause Counter Helix to proc multiple times.
* This can get worse if axe has Blade Mail, which then returns all damage to Alchemist himself.
* Axe's abilities can pierce through Black King Bar, which is a common item for Alchemist.
* Berserker's Call grants Axe a huge bonus armor, which greatly counters Alchemist's physical damage for the most part.

* 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.

* Berserker's Call prevents Sven from bursting his targets before Axe can interfere. The worst kind of opponent for Sven is one who can stop him from attacking who he wants to, which is exactly what Axe does.
* Culling Blade may finish off Sven before he has the chance to lifesteal or run with Warcry.
* Axe is a very common Blade Mail carrier which will make very short work of a Sven with God's Strength activated.

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

* Heroes with burst damage of their own won't be afraid to go toe to toe with Void Spirit, like Ursa, Lifestealer, or Axe.

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

* Troll Warlord's high attack speed means Counter Helix will proc extremely frequently even without creeps near him. This, combined with a Blade Mail means Axe can easily solo kill Troll Warlord even in later stages of the game.
* Battle Trance does not save Troll Warlord from a Culling Blade.
Additional:
* Troll Warlord has significant attack speed due to Fervor and Battle Trance, giving Axe a higher chance to proc Counter Helix and seriously injure Troll Warlord due to his relatively low maximum health.
* Axe often purchases Blade Mail, which can help Axe turn Troll Warlord's farm and high physical damage against him. The bonus armor provided by Berserker's Call means that Troll Warlord will take a lot more damage than Axe.
* Culling Blade is still capable of killing Troll Warlord during Battle Trance if his HP is low enough.

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

* Berseker's Call catches Slark in Shadow Dance, wasting its duration and preventing him from escaping to regenerate.
* Unlike most disables, Dark Pact cannot dispel Berserker's Call, and the output damage would be returned by Blade Mail.
Additional:
* Berserker's Call forces Slark to attack him, even during Shadow Dance.
* Counter Helix will hit Slark in Shadow Dance. It also triggers frequently against Slark's high attack speed provided by Essence Shift stacks.
* Culling Blade finishes off Slark before he gets a chance to slip away and regenerate his health, preventing him from playing the typical hit-and-run style.

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

Additional:
* Nethertoxin negates 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 who rely on summons, illusions or clones will trigger Counter Helix more often, thus taking more damage: Meepo, Lycan, Phantom Lancer

Additional:
* The combination of Counter Helix and Berserker's Call can disable multiple Meepos and deal heavy area damage.
* Axe's natural high survivability makes it difficult to burst him down with Poof or chip away at his health with Ransack.

* Nethertoxin 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.

* Axe can easily close the distance to Sniper with Blink Dagger.
* With Berserker's Call in combination with Counter Helix and Battle Hunger, Axe can make short work of Sniper, finishing him off easily with Culling Blade due to his low HP & high attack speed in the late game.

* Nethertoxin breaks Sniper's passives.
* Viper Strike together with Poison Attack can slow Sniper and tears through his low health and mobility.

* Berserker's Call prevents Anti-Mage from escaping with Blink, and works well with Blade Mail against Anti-Mage's relatively low health.
* Counter Helix often triggers even if Axe's depleted of mana, which will make Anti-Mage take more damage than he's dealing and deals pure damage, ignoring the protection from Counterspell.
* Axe's low mana pool makes him a bad target for using Mana Void.
* Axe's high base health regeneration allows him to dominate the lane against Anti-Mage, especially with a support.
Additional:
* Berserker's Call is one of the most reliable ways to lock down Anti-Mage, preventing him from Blinking away.
* Anti-Mage's high attack speed, along with illusions from Manta Style, triggers Counter Helix continuously.
* Axe's low mana pool and high health pool makes Mana Void deal very little damage to Axe.

* 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.

* Heroes who continue dealing damage while being stunned: Luna, Razor, Axe, Bristleback, Leshrac,

* Heroes that can slow Charge of Darkness by a huge amount: Venomancer, Viper, Dazzle, Arc WardenLion

* Axe forces Bristleback to turn around with Berserker's Call, allowing allies to attack him without fear of his passive.

* Nethertoxin disables Bristleback's passive.
* Viper Strike and Poison Attack slow down Bristleback's movement speed so he's unable to get out from Nethertoxin.
Additional:
* Nethertoxin disables 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.

* 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.
* Corrosive Skin reduces damage from Dragon Fire and inflicts damage to him.
* Nethertoxin 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.
* Nethertoxin mitigates 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.

* Every single one of Axe's abilities can affect Muerta during her Pierce the Veil
* While Muerta can do much damage to highly armored units, Axe has a larger health pool compared to Muerta and can activate Berserker's Call and an activated Blade Mail to quickly kill Muerta due to her high right click damage.
* Muerta often builds high attack speed making Counter Helix have a high chance to proc.

* Phantom Strike's extra attack speed will cause Phantom Assassin to trigger Counter Helix more often, which can be fatal for Phantom Assassin. Jumping on Axe with Phantom Strike is not a good idea for Phantom Assassin at all as it makes her a seriously easy target for a counter-initiation with Berserker's Call and Blade Mail.
* Most of Axe's abilities pierce Black King Bar, allowing him to lock down Phantom Assassin at any time.
* Berserker's Call greatly reduces Phantom Assassin's ability to crit hard against Axe, and may cause her to kill herself when used with Blade Mail. Berserker's Call can also affect Phantom Assassin even if she has Black King Bar active as Berserker's Call can fully pierce spell immunity, making Berserker's Call one of the best abilities in the game against heroes like Phantom Assassin who wants to kill opponents quickly without being interrupted.
* Culling Blade can often kill Phantom Assassin before she can do anything due to her low health and strength gain. And every time Culling Blade successfully kills Phantom Assassin or any of her teammates, Axe gains permanent armor from it, which in combination with armor items that Axe often purchases like Blade Mail, Crimson Guard, Assault Cuirass and Shiva's Guard can make Phantom Assassin's attacks only tickle Axe.
* Aghanim's Shard upgraded Counter Helix can weaken Phantom Assassin's damage output, and if her attack damage is weak, Coup De Grace will also suffer from attack damage reduction as well.
Additional:
* Phantom Strike's extra attack speed will cause Phantom Assassin to trigger Counter Helix more often, which can be fatal for Phantom Assassin in the early game. Jumping on Axe with Phantom Strike is not a good idea for Phantom Assassin at all as it makes her a seriously easy target for a counter-initiation with Berserker's Call and Blade Mail.
* Most of Axe's abilities pierce Black King Bar, allowing him to lock down Phantom Assassin at any time.
* Berserker's Call greatly reduces Phantom Assassin's ability to crit hard against Axe, and may cause her to kill herself when used with Blade Mail. Berserker's Call can also affect Phantom Assassin even if she has Black King Bar active as Berserker's Call can fully pierce spell immunity, making Berserker's Call one of the best abilities in the game against heroes like Phantom Assassin who wants to kill opponents quickly without being interrupted.
* Culling Blade can often kill Phantom Assassin before she can do anything due to her low health and strength gain. And every time Culling Blade successfully kills Phantom Assassin or any of her teammates, Axe gains permanent armor from it, which in combination with armour items that Axe often purchases like Blade Mail, Crimson Guard, Assault Cuirass and Shiva's Guard can make Phantom Assassin's attacks only tickle Axe.
* Blade Mail is an item that Axe purchases every game, and which can be used to turn Phantom Assassin's critical strikes from Coup De Grace against herself. This can become even worse if she's affected by Berserker's Call, as she has no way to stop attacking.
* Aghanim's Shard upgraded Counter Helix can weaken Phantom Assassin's damage output, and if her attack damage is weak, Coup De Grace will also suffer from attack damage reduction as well.
* Axe just has to be careful about Fan of Knives from Aghanim's Shard and Coup De Grace, as Fan of Knives can disable Counter Helix, even if Axe is spell immune.

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

* Unleash ensures that Axe's Counter Helix procs many times, even if he is stunned by Dispose.
* Aghanim's Shard allows Counter Helix to reduce the attack damage of anyone it strikes. Combined with Unleash causing to proc frequently, Marci will not be dealing significant damage as she attacks Axe over time.
* Axe doesn't worry about the damage from Unleash if he activates Berserker's Call beforehand. If he had activated Blade Mail or Mjollnir (or even both) as Marci attacks him, he will turn Unleash's high attack speed and damage against her.
* Usually, Axe would prefer to jump on his opponent to be more effective. Rebound does Axe a favor, bringing Marci within his most effective range.

* 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 traditionally forgoes health and armor items for damage. Outside of Black King Bar, Viper will almost always be able to kill her when Refraction is down.

* 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.

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

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

* 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.

* Nethertoxin 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.
* Tidehunter relies on the threat of Ravage, which has an obscenely long cooldown. Viper can exploit the downtime with his short cooldowns.

* 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.

* 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:
* Nethertoxin prevents 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.

* Corrosive Skin minimizes the damage from Impale and Mana Burn.
* Nyx Assassin cannot survive several poison damage-over-time, even Spiked Carapace is activated.

* 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.

* Nethertoxin prevents buildup of Fiery Soul stacks.
* Corrosive Skin provides magic resistance against Lina's spells.
* Poison Attack and Viper Strike can burn away Lina's small health pool.

* Nethertoxin disables Dawnbreaker's Luminosity|Dawnbreaker. 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.

* 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.
* Nethertoxin disables Aftershock, which removes the stun and bonus damage from Enchant Totem and Echo Slam.

* Berserker's Call forces Dark Willow to attack, cancelling Shadow Realm.

* 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.

* 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:
* Nethertoxin disables 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.

* False Promise will not save an ally from Culling Blade if their health is low enough.
* Fate's Edict, offensively or defensively, does little to protect Oracle's allies from the majority of Axe's damage.

* 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 Nethertoxin, leaving Razor without faster MS.
* Static Link's damage drain doesn't bother Viper a lot as most of his early to mid game damage is magical.

* Culling Blade ignores the protection from Shallow Grave, and will kill any target whose health is low enough. This makes Axe one of the hardest counters to Dazzle, and he neutralizes one of Dazzle's most important abilities.
Additional:
* Culling Blade kills any target under the health threshold, even through Shallow Grave.

* 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 gap closing abilities will be easy targets for Berserker's Call: Phantom Assassin, Faceless Void, Slark, Chaos Knight, Morphling, Queen of Pain

Additional:
* Berserker's Call prevents Queen of Pain from escaping with Blink and also pierces her Black King Bar.
* Due to her fast attack speed from Mjollnir, it will quickly trigger Counter Helix.
* Culling Blade finishes off Queen of Pain's low health pool before she gets a chance to escape, preventing her from playing the hit-and-run style often associated with Queen of Pain.

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

* Heroes with gap closing abilities will be easy targets for Berserker's Call: Phantom Assassin, Faceless Void, Slark, Chaos Knight, Morphling, Queen of Pain

* Heroes with other kind of disables that pierce spell immunity can hold Pangolier in place during Rolling Thunder: Axe, Beastmaster, Enigma, Magnus, Pudge, Batrider, Bane, Winter Wyvern

* Windrun does not provide protection against Counter Helix and Berserker's Call. Her fast attack speed with Focus Fire will also quickly trigger Counter Helix multiple times.

* 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 high armor and durability can be exceptionally hard for Bloodseeker to bring down: Dragon Knight, Axe

* Heroes who rely on fast attack speed will also trigger Counter Helix frequently: Faceless Void, Troll Warlord, Anti-Mage, Juggernaut, Arc Warden, Morphling

Additional:
* Berserker's Call pierces spell immunity, making a Blade Fury teleport escape impossible. It's very useful against Omnislash as well.
* Juggernaut's low base health and high attack speed causes him to take a lot of damage from Counter Helix.
* Axe is a common Blade Mail and Blink Dagger carrier making him a very big potential threat before Juggernaut get his items.

* 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' 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.

* Heroes that are hard to gank: Axe, Death Prophet, Phantom Lancer

* 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.

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

* Nethertoxin prevents Timbersaw from gaining stacks on Reactive Armor.

* Berserker's Call and Counter Helix will still hit targets inside of a defensive Sprout.
* Counter Helix clears treants in no time.
* Nature's Prophet's low damage is unlikely to hurt Axe until the very late game.
* Nature's Prophet's low mobility makes him very easy for Axe to chase down or initiate on, especially when affected by Battle Hunger.

* Berserker's Call forces Drow Ranger to attack Axe up close, disabling her Marksmanship bonus.
* Counter Helix occurs more often with Drow Ranger's high attack speed.
* Culling Blade is a dangerous ability against a low health hero like Drow Ranger.

* Heroes with gap closing abilities will be easy targets for Berserker's Call: Phantom Assassin, Faceless Void, Slark, Chaos Knight, Morphling, Queen of Pain

Additional:
* Berserker's Call allows Axe to lock down Chaos Knight and his illusions even through Black King Bar.
* Counter Helix combined with Blade Mail clears illusions out in no time.

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

* Jumping on Axe with Waveform will make Morphling an easy target for a counter-initiation with Berserker's Call.
* Morphling is often played at low health to maximise the bonuses from Attribute Shift (Agility Gain), and also because his abilities cost health to use. This makes him especially vulnerable to Culling Blade.
* However, Morphling is common Linken's Sphere carrier to block Culling Blade forces Axe to use Battle Hunger to pop the Spell Block first.
* Attribute Shift (Agility Gain) gives Morphlig no protection against the pure damage of Culling Blade. Its attack speed bonus also means that Counter Helix will proc more often.

* Terrorblade's low base health and lack of mobility make him an easy target for Axe to initiate on, and kill.
* Counter Helix will trigger from, and destroy many of Terrorblade illusions.
Additional:
* Berserker's Call and Counter Helix together can be devastating to Terrorblade, especially if Terrorblade has a lot of illusions. Their high attack speed will trigger Counter Helix a lot, and the pure damage will quickly slice through Terrorblade's low health and kill his illusions. More importantly, the Berserker's Call can pierce through spell immunity from Black King Bar, Terrorblade's only survival item besides Manta Style which cannot be used to dispel Berserker's Call. With enough burst damage by Axe's teammates, Terrorblade can be finished off even before taunt duration runs out and he gets a chance to save himself with Sunder.
* Culling Blade can finish off Terrorblade before he has the chance to Sunder due to his low health in the early to mid game. And every time Terrorblade or any of his allies are successfully killed by Culling Blade, Axe permanently gains armor from it, which in combination with armor items that Axe often purchases like Blade Mail, Crimson Guard, Assault Cuirass and Shiva's Guard can make Terrorblade's attacks only tickle Axe, even during Metamorphosis.
* Terrorblade's low base health and lack of mobility make him an easy target for Axe to initiate on, and kill.

* 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 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.

* 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.

* 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.

* 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 Nercophos spells that deal magical damage, which is Necrophos's only source of damage.
Additional:
* Nethertoxin 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.

* Berserker's Call catches Phantom Lancer when he is hidden among his illusions.
* Counter Helix quickly destroys Phantom Lancer's illusion army. The more illusions there are, the more often Counter Helix is triggered.
* Phantom Lancer's low early game health makes him an easy target for Culling Blade.
Additional:
* Berserker's Call helps locking down Phantom Lancer in a group of illusions.
* Counter Helix combined with Blade Mail clears Phantom Lancer's illusions quickly.
* Phantom Lancer's low health in the early game makes him a frequent target for Culling Blade.

* Berserker's Call is one of the best ways to lock down Weaver before he has a chance to use Time Lapse. It can also catch Weaver in Shukuchi.
* Weaver's high attack speed, along with high attack damage from Geminate Attack, triggers Counter Helix continuously and the output damage would be returned by Blade Mail.
Additional:
* Berserker's Call is one of the best ways to lock down Weaver before he has a chance to use Time Lapse. It can also catch Weaver in Shukuchi.
* Due to his fast attack speed from Geminate Attack and items that give attack speed, Counter Helix will activate a lot, and the damage would be returned by Blade Mail, which hurts Weaver far more than it hurts Axe.
* Culling Blade can finish off Weaver's low health pool before he escapes with Shukuchi and Time Lapse.
* Battle Hunger is a good tool to pop Weaver's Linken's Sphere due to its low cooldown.

* 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.

* 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.

* Axe will destroy her illusions by proccing Counter Helix more often due to him being hit by more attacks.

* 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.

* 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.

* Nethertoxin breaks Fury Swipes, making Viper a decent counter to Ursa in a laning stage.
* Viper Strike is a strong, undispellable slow, making it much easier to kite Ursa for everyone.

* Berserker's Call can catch Broodmother in her web, as well as groups of spiderlings. This is particularly effective when Broodmother attempts to push towers with her spiderlings.
* Counter Helix destroys spiderlings very quickly, and earns Axe a good deal of gold.
Additional:
* Berserker's Call forces Broodmother and her spiderlings to attack, allowing for large amounts of pure damage to be done through Counter Helix.

* Melee heroes who rely on summons, illusions or clones will trigger Counter Helix more often, thus taking more damage: Meepo, Lycan, Phantom Lancer

Additional:
* Berserker's Call can keep Lycan in place during his Shapeshift even through Black King Bar.
* Counter Helix is very effective against Lycan because of his summons.
* Culling Blade will prevent Lycan from running away with Shapeshift when he drops low.