Warlock
* Warlock's signature 
Chaotic Offering can be devastating if stolen and dropped on multiple heroes.
* Telekinesis interrupts 
Upheaval when used on Warlock. Alternatively, Rubick can also cast this on a naerby creep or hero and drop them near Warlock to interrupt its channeling. When upgraded with 
Aghanim's Shard, Rubick can also use it to save an ally (or himself) from its area slow and damage.
* 
Fatal Bonds provides Rubick with a decent farming and harassing tool in the early game.
* 
Shadow Word provides some utility by healing Rubick and his team, and also as a harassment tool when used on enemies in the laning stage.
* Upheaval slows and damages enemies in an area, and it works exactly the same when casted by Rubick. Furthermore, he can extend its range and debuff amplification with Arcane Supremacy.
* A stolen Chaotic Offering can also be used to interrupt Upheaval while Telekinesis is on cooldown.
* It is advised to build items around Chaotic Offering as Rubick. 
Aghanim's Scepter, 
Octarine Core and 
Refresher Orb are all legitimate item choices.
Additional:
* All of Warlock's abilities are worthy choices for Rubick to 
Spell Steal, primarily Chaotic Offering. Furthermore, stolen abilities are also affected by the increased cast range and spell amplification from 
Arcane Supremacy.
* 
Telekinesis interrupts Upheaval when casted on Warlock, or to save allies (or himself) from its area slow and damage with Aghanim's Shard.
* Bear in mind that Warlock likes to cast his abilities in quick succession, so the time window left for Rubick to steal Warlock's ultimate can be short.
Viper
* If Rubick can use Spell Steal to take 
Nethertoxin, he will be able to disable 
Corrosive Skin, reducing much of Viper's durability.
* He can also steal 
Viper Strike, which can be used to hinder a hero on your team (or multiple heroes, if Rubick has Aghanim's Scepter).
Warlock
* Heroes who rely on summons will see them destroyed easily by Overwhelming Odds: 
Lycan, 
Arc Warden, 
Warlock, 
Chen
Viper
* 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.
Warlock
* 
Shapeshift allows Lycan to escape from Upheaval with maximum movement speed.
* Warlock doesn't have a good solution to deal with Lycan's wolves from 
Summon Wolves.
Viper
* Heroes who do not have nor rely on passive abilities make Nethertoxin much less effective: 
Clinkz, 
Pugna, 
Nature's Prophet, 
Dark Seer, Lycan, 
Tusk
Warlock
* Heroes that rely on summons will suffer against Ion Shell, which kills them very quickly: 
Beastmaster, 
Broodmother, 
Enigma, Nature's Prophet, 
Visage, Warlock, 
Wraith King.
Additional:
* 
Surge allows for Dark Seer and his allies to escape from Upheaval due to it ignoring any slow.
Viper
* Heroes who do not have nor rely on passive abilities make Nethertoxin much less effective: Clinkz, Pugna, Nature's Prophet, Dark Seer, Lycan, Tusk
Viper
* Viper is kind of a mixed package. Tinker is very good against him. but stands a better chance against him than most heroes.
* Viper has a high innate magic resistance, but relies on his primary attacks to really deal damage. making Laser an effective way to save allies from him, and deal damage. Keep in mind that his Corrosive Skin will prevent Tinker from blinking.
* Viper's Viper Strike and Poison Attack will also have a hard time damaging allies through Tinker's constant casting of 
Defense Matrix.
* Viper has no solutions to cancel 
Rearm nor any of Tinker's escape attempts with 
Boots of Travel
* However, if Viper gets a jump on Tinker first. Tinker will unlikely survive versus Viper.
Viper
* Viper has no disable, which means he has no way of preventing Morphling from escaping from any of his abilities or keep him inside Nethertoxin.
* Viper is almost exclusively damage over time, which is weak against Morphling due to 
Attribute Shift (Strength Gain). Additionally, Morphling has no passive abilities, reducing Nethertoxin's effectiveness against him even further.
* Morphling can turn into Viper himself, allowing him to use any of Viper's abilities against him (excluding Viper Strike). This is particularly bad due to the fact that Viper is already a very slow hero, making Poison Attack and Corrosive Skin's slows especially difficult to deal with.
Viper
* Viper's lack of escape and durability means he can be ran over in a laning stage by 
Spawn Spiderlings.
* Broodmother can bring Viper down quickly with 
Insatiable Hunger activated.
Viper
* Pugna's 
Decrepify allows him to save allies from being ganked by Viper, since Viper mostly relies on direct attacks in order to deal damage.
* 
Nether Ward can discourage Viper from spamming his abilities.
* Viper's damage over time is not enough to kill Pugna as he will have more than enough time to save himself (or his allies) with 
Life Drain and Viper has no solutions to cancel it.
* Pugna has no passive abilities, which renders Nethertoxin nearly useless.
Viper
* Clinkz does not have any passive abilities at all, making Nethertoxin nearly useless.
* Viper's Corrosive Skin provides no protection against Clinkz's physical damage output.
Warlock
* A pre-placed 
Fire Remnant allows Ember Spirit to escape Upheaval.
* 
Flame Guard blocks Shadow Word's damage.
* 
Sleight of Fist allows Ember Spirit to attack from outside of Upheaval's range, and 
Searing Chains lets him interrupt it.
Viper
* Almost all of Viper's damage revolves exclusively around single-target damage-over-time effects. Furthermore, without any hard disables, Terrorblade can almost always get a Sunder off.
* Viper has low mobility and Corrosive Skin doesn't protect against physical damage, which means that Terrorblade under Metamorphosis can quickly kill Viper.
Additional:
* Viper's damage over time and lack of disables makes him easy to 
Sunder.
* Viper's physical damage is mitigated by Terrorblade's high armor.
* Terrorblade under 
Metamorphosis can quickly kill Viper with heavy physical damage.
Viper
* The Keeper of the Light easily farms on the line against the Viper, due to the fact that it has a long-range 
Illuminate, and the Viper, in turn, cannot use its advantage of dominance on the center line, due to the fact that it does not reach the Keeper of the Light
Additional:
* The Keeper of the Light easily farms on the line against the Viper, due to the fact that it has a long-range Illuminate, and the Viper, in turn, cannot use its advantage of dominance on the center line, due to the fact that it does not reach the Keeper of the Light
Warlock
* 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.
Viper
* As Viper focuses on single-target damage, he has trouble fighting off Phantasm illusions.
* Reality Rift counteracts Viper's slows and reduces his already low durability against physical damage.
Additional:
* Viper has no response to the standard initiation combo of 
Reality Rift into 
Chaos Bolt.
* 
Phantasm and 
Chaos Strike can eliminate Viper almost instantly with it's damage output.
* Besides Nethertoxin, Viper has no other ways of dealing with Phantasm.
Viper
* Heroes with Attack speed decreasing skills: 
Jakiro, 
Viper 
Lich
Viper
* Viper Strike can be countered through Snowball, wasting Viper's mana through his ultimate. It's Viper Strike's break is also useless because he has no passive abilties at all. And to make things worse, Viper Strike cannot disable 
Walrus PUNCH! because it's an auto-cast ability
* As Tusk is a natural 
Silver Edge wielder, he can use it to disable Viper's magic resistance from Corrosive Skin, and make him vulnreable to his other allies.
Viper
* 
Ball Lightning allows Storm Spirit to escape through Viper Strike, wasting Viper's mana.
* It's also very easy to wait out the duration of Nethertoxin's break.
Viper
* Even though Luna has a hard time laning against Viper due to Nethertoxin being able to disable 
Moon Glaives and 
Lunar Blessing, Luna can take out Viper once she builds either 
Black King Bar or Silver Edge which will allow her to attack Viper freely.
* 
Eclipse can often finish off Viper from early-to-mid stages of the game before he can retaliate as Corrosive Skin gives little magic resistance to him early on.
* 
Manta Style is an item that Luna commonly buys in most of the games, which lets her disjoint Viper Strike. Additionally, illusions from Manta Style can make Viper waste time attacking them.
Additional:
* Even though Luna has a hard time laning against Viper due to Nethertoxin being able to disable Moon Glaives and Lunar Blessing, Luna can take out Viper once she builds either Black King Bar or Silver Edge which will allow her to attack Viper freely.
* Eclipse can often finish off Viper from early-to-mid stages of the game before he can retaliate as Corrosive Skin gives little magic resistance to him early on.
* Manta Style is an item that Luna commonly buys in most of the games, which lets her disjoint Viper Strike. Additionally, illusions from Manta Style can make Viper waste time attacking them.
Viper
* Although Viper Strike cannot be dispelled by Doppelganger, Viper's lack of mobility and AoE damage makes him an easy target for Phantom Lancer.
* Viper's various slows do not work against 
Phantom Rush.
* Although Phantom Lancer should be wary due to Nethertoxin applying Break.
Additional:
* Phantom Lancer can overwhelm Viper with spawned illusions from 
Spirit Lance and 
Doppelganger. In addition, 
Diffusal Blade, a core item on Phantom Lancer, burns Viper's limited mana pool, reducing his potential poison damage.
* Viper's various slows do not work against Phantom Rush. Additionally, it is almost impossible to keep Lancer inside Nethertoxin's radius in order to disable the passive.
Viper
* Naga Siren can easily disjoint, and dispel Corrosive Skin with Mirror Image.
* Since Viper is mostly a single-target hero, he will not have almost any chance against Naga Siren because she is an illusion based hero.
* Viper has no burst damage, so Naga Siren will have plenty of time to use Aghanim's Shard upgraded 
Song of the Siren heal her allies before Viper can finish them off.
Viper
* Viper cannot interrupt heroes with powerful channeling abilities: 
Bane, Enigma, 
Shadow Shaman, Warlock
Viper
* Heroes who rely on magical damage resistance may have a hard time laning against Dazzle as all of Dazzle's abilities deal physical damage instead of magical: 
Anti-Mage, 
Huskar, Viper.
Warlock
* 
Mana Break prevents Warlock from casting his spells, particularly in the laning phase.
* 
Blink allows Anti-Mage to escape from Upheaval.
* 
Counterspell reduces damage from Shadow Word and Warlock's Golem's 
Permanent Immolation passive. Additionally, it can reflect Shadow Word and Fatal Bonds.
* 
Mana Void deals heavy damage after Anti-Mage has drained Warlock's large mana pool.
Viper
* Heroes that can drain mana negatively affect Viper's ability to use Poison Attack, Nethertoxin and Viper Strike: 
Lion, Anti-Mage
Viper
* 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.
Warlock
* Heroes with channeling spells are very easy targets for Jakiro's abilities: 
Crystal Maiden, 
Dawnbreaker, Enigma, 
Pudge, 
Shadow Fiend, Shadow Shaman, Warlock.
Warlock
* Because all of Warlock's abilities are active abilities, silences can make his impact in fights minimal. Be cautious of heroes that carry silences like 
Death Prophet, 
Puck, and the aforementioned 
Silencer.
Viper
* Ranged heroes will have a hard time hitting enemies inside Magnetic Field: Silencer, Viper.
Viper
* Heroes who do not have nor rely on passive abilities make Nethertoxin much less effective: Clinkz, Pugna, Nature's Prophet, Dark Seer, Lycan, Tusk
Viper
* Illusion or summon-based heroes can be a problem to Viper due to his lack of AoE damage: 
Naga Siren, 
Phantom Lancer, Beastmaster
Viper
* Viper's Nethertoxin cannot disable 
Reincarnation, which could put him in disadvantage against Wraith King if his whole team is with him.
* In addition, Viper doesn't like buying Diffusal Blade, which is the only item that can help him against Wraith King.
* Wraith King's high burst damage allows him to kill Viper before being killed.
Viper
* Melee heroes with low mobility can be kited and killed by Viper: 
Treant Protector, 
Kunkka, 
Alchemist, 
Troll Warlord, Wraith King, 
Tiny, 
Sven.
Viper
* Viper is an agility hero, and his item build mostly includes agility items, so Natural Order can be devastating, removing all armor and greatly decreasing the effectiveness of Corrosive Skin, weakening Viper's magic resistance. Additionally, Echo Stomp and Earth Splitter deal both magical and physical damage, and can help bringing Viper down fast.
* Aghanim's Scepter may be necessary to take Viper down due to Nethertoxin's break.
Warlock
* While heroes with strong mobility are able to get close or flee from Upheaval, heroes with no escaping abilities or that lack long disables will perish against Warlock. Once the Warlock Golem lands with its stun, its hardly possible to escape when he casts Upheaval. Notable examples: Huskar, 
Drow Ranger, Lion, 
Elder Titan, etc.
Viper
* 
Rage ignores all of Viper's magical damage, although Viper Strike can pierce spell immunity and slows him down.
* 
Feast and 
Open Wounds from Aghanim's Shard can be combined to heal through Viper's physical damage.
* Aghanim's Scepter upgraded 
Infest can be used to disarm Viper, preventing him from using Poison Attack on Lifestealer's allies.
Warlock
* Heroes with summons: Lycan, Broodmother, Visage, Nature's Prophet, Warlock.
Viper
* 
Enfeeble weakens Viper's attack damage, any healing he receives and his cast range, which makes him unable to harass enemy heroes with Nethertoxin, Poison Attack and Viper Strike.
* 
Brain Sap allows Bane to heavily harass Viper, damaging him while healing Bane, which allows Bane to fight back against Viper's damage over time output, even through debuff immunity from Black King Bar.
* Viper's Corrosive Skin is useless against Bane as all of his damaging abilities deal Pure damage.
* Viper has no solutions to cancel 
Fiend's Grip and in addition, he hates buying disabling items like 
Eul's Scepter of Divinity.
Additional:
* Enfeeble weakens Viper's attack damage, any healing he receives and his cast range, which makes him unable to harass enemy heroes with Nethertoxin, Poison Attack and Viper Strike.
* Viper's Corrosive Skin is useless against Bane as all of his damaging abilities deal Pure damage.
* Viper has no solutions to cancel Fiend's Grip and in addition, he hates buying disabling items like Eul's Scepter of Divinity.
Warlock
* Heroes with illusions and summons can swarm and overwhelm Bane, who has no area abilities to deal with them outside from Aghanim's Shard upgraded Brain Sap: Broodmother, Chaos Knight, Naga Siren, Nature's Prophet, Phantom Lancer, 
Terrorblade, Visage, Warlock, Wraith King.
Warlock
* Because Warlock's abilities are all active abilities, Silencer can make his impact minimal.
* 
Arcane Curse prevents Warlock from using his abilities without increasing it's duration, which since all of Warlock's abilities are actives it is very effective against him.
* 
Last Word can prevent Warlock from casting his Fatal Bonds, Chaotic Offering, and Upheaval combo.
* 
Global Silence can nullify Warlock's impact in fights by preventing him from casting Fatal Bonds and Chaotic Offering, or by interrupting his Upheaval.
Viper
* 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.
Viper
* Voodoo Restoration heals to counter damage over time of Viper abilities.
* Viper has no way to cancel Death Ward, even through 
Rod of Atos.
Warlock
* Channeling heroes will not go well against Warlock, especially those who build Black King Bar as Warlock's ultimate ability stun goes through spell immunity. E.g.: Crystal Maiden, 
Witch Doctor, Enigma, etc.
Warlock
* Ghostship helps your team soak up damage from Chaotic Offering and hit summons hard.
* Tidebringer clears summons later in the game.
* Most of your spells can interrupt Upheaval.
Viper
* Melee heroes with low mobility can be kited and killed by Viper: Treant Protector, Kunkka, Alchemist, Troll Warlord, Wraith King, Tiny, Sven.
Warlock
* Upheaval does not interrupt Slark too much, as he can just Pounce out of the area.
* Fatal Bonds and Shadow Word can be dispelled by Dark Pact.
Viper
* 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).
Warlock
* With God's Strength, Warlock's Golem from Chaotic Offering will go down in a matter of seconds. The two weaker golems granted by Aghanim's Scepter will fare worse due to 
Great Cleave hitting both.
* Aghanim's Scepter upgraded 
Storm Hammer Aghanim's Scepter can dispel Shadow Word.
Additional:
* 
God's Strength combined with Great Cleave destroys Chaotic Offering golems within seconds.
* 
Warcry gives Sven and his allies armor to help against Warlock's Golem's heavy physical damage and movement speed to help escape Upheaval.
* Storm Hammer disrupts Upheaval.
Viper
* Melee heroes with low mobility can be kited and killed by Viper: Treant Protector, Kunkka, Alchemist, Troll Warlord, Wraith King, Tiny, Sven.
Viper
* 
Windrun evades Poison Attack and counteracts the slow.
* Viper's low mobility makes him an easy 
Shackleshot target.
* 
Focus Fire grants Windranger significant physical damage output to quickly wear Viper down.
* 
Powershot is a strong harassment and zoning tool against Viper in lane.
Viper
* 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.
Warlock
* Warlock Golems do plenty of physical and pure damage to bring down Huskar when he is at low health. Warlock is always a hazard for Huskar to initiate by using 
Life Break, because Chaotic Offering can stun him instantly, even when Black King Bar is activated, and allows Warlock's team to gather their wit and retaliate.
* After using Life Break to jump in, Huskar will not have any means to escape Upheaval. Which since he is an attack-dependent hero, this will nullify his impact in fights.
Viper
* 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.
Warlock
* Fatal Bonds links the Meepos together, which combined with area of effect damage or Cleave will be devastating.
Viper
* 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.
Warlock
* 
Enchant can not control golem Chaotic Offering from Warlock.
Viper
* Heroes with break can disable Untouchable for a while: 
Doom and Shadow Demon (via Aghanim's Scepter), Viper, Shadow Shaman with Hex Breaks talent.
Warlock
* Heroes with channeling spells because Shadow Fiend has nothing to cancel channeling outside of Requiem of Souls: Bane, Enigma, Pudge, Shadow Shaman, Dawnbreaker, Warlock, Crystal Maiden.
Additional:
* Because Shadow Fiend lacks escaping mechanisms, and is dependent on fair positioning for channeling 
Requiem of Souls, it's easier for Warlock with his long range crowd control abilities to lock Shadow Fiend down for his team.
Viper
* 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.
Warlock
* Warlock often stays back and counter-initiates by dropping his Chaotic Offering on Earthshaker and his allies.
Viper
* 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.
Warlock
* Heroes with illusions and summons can be hard for Phantom Assassin to deal with, as she lacks any AoE abilities to deal with them without items: Broodmother, Phantom Lancer, Chaos Knight, Lycan, Naga Siren, Shadow Shaman, Visage, Nature's Prophet, Terrorblade, Warlock, Wraith King.
Viper
* Heroes that can apply early pressure before Phantom Assassin has farm are massive threats: 
Axe, Viper, 
Meepo, Jakiro, Pugna, 
Slark, Venomancer etc.
Warlock
* Illusion and heroes with summons are difficult to kill with Chen's single-target offensive spells: Terrorblade, Phantom Lancer, Chaos Knight, Broodmother, Naga Siren, Lycan, Visage, Beastmaster, Warlock, Wraith King. And even though Chen can convert enemy summons with Holy Persuasion, their much greater numbers will often overwhelm Chen and his creeps.
Viper
* 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.
Warlock
* Channeling heroes will not go well against Warlock, especially those who build Black King Bar as Warlock's ultimate ability stun goes through spell immunity. E.g.: Crystal Maiden, Witch Doctor, Enigma, etc.
Viper
* 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
* 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.
Viper
* 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.
Warlock
* Warlock has strong counter initiation which reduces Marci's effectiveness throughout the game.
* Fatal Bonds cancels Blink Dagger, which means Marci can move in and out of fights less effectively.
* Chaotic Offering paired with Upheaval provides a ministun, a movement slow and paired with Fatal Bonds has the potential to deal a lot of damage to Marci while she jumps on a target. The ministun also means that Marci will have a harder time casting Rebound. If Warlock does build Aghanim's Scepter and Refresher Orb, the physical damage from Golems will overwhelm Marci, especially when played as a support.
Viper
* Viper Strike prevents Timbersaw from gaining stacks on Reactive Armor.
Viper
* 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.
Warlock
* Chaotic Offering's vast area-effect can destroy trees and stun Hoodwink.
* Upheaval makes retreating with 
Scurry difficult.
Viper
* 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
* 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
* 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.
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.
Viper
* 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.
Viper
* 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.
Viper
* Poison Attack makes it hard for Void Spirit to lane against him.
* Corrosive Skin reduces the magical damage from Void Spirit's spells.
Viper
* 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
* Viper Strike breaks Multicast.
* Corrosive Skin minimizes the damage from Ignite and Fireblast.
Viper
* 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.
Viper
* 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.
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.
Viper
* 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.
Viper
* 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.
Viper
* Corrosive Skin minimizes the damage Viper takes from all of Disruptor's skills.
Viper
* 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.
Viper
* 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.
Warlock
* Fragile supports with low armor are always a good prey, also her Psionic Trap will wear down most attempts to flee with their built-in disables: Silencer, Crystal Maiden, Warlock, 
Ancient Apparition, 
Grimstroke, Witch Doctor
Warlock
* 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.
Additional:
* Warlock can cast Upheaval when Templar Assassin uses 
Meld, preventing her from escaping at the right moment.
* Warlock can also send his Warlock Golem near where she used Meld, preventing escape by Blink Dagger due to the Warlock Golem's Permanent Immolation.
* Warlock's Golem's Permanent Immolation will burn away 
Refraction with its damage over time.
Viper
* 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.
Viper
* 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.
Viper
* 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.
Viper
* 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.
Viper
* 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.
Viper
* Melee heroes with low mobility can be kited and killed by Viper: Treant Protector, Kunkka, Alchemist, Troll Warlord, Wraith King, Tiny, Sven.
Viper
* Melee heroes with low mobility can be kited and killed by Viper: Treant Protector, Kunkka, Alchemist, Troll Warlord, Wraith King, Tiny, Sven.
Warlock
* 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.
Warlock
* Heroes with summons and illusions as Spirit Breaker has no strong AoE capabilities to deal with them: Chaos Knight, Phantom Lancer, Terrorblade, Naga Siren, Broodmother, Warlock, Visage, Nature's Prophet, Shadow Shaman, Lycan, Wraith King.
Viper
* Heroes that can slow Charge of Darkness by a huge amount: Venomancer, Viper, Dazzle, Arc Warden, Lion, Huskar, Shadow Shaman, Visage, 
Undying, Jakiro.
Viper
* 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.
Viper
* Heroes who can harass Omniknight out of lane will keep him weak in the mid game: Viper, Venomancer, Clinkz.
Warlock
* While heroes with strong mobility are able to get close or flee from Upheaval, heroes with no escaping abilities or that lack long disables will perish against Warlock. Once the Warlock Golem lands with its stun, its hardly possible to escape when he casts Upheaval. Notable examples: Huskar, Drow Ranger, Lion, Elder Titan, etc.
Warlock
* Heroes with both illusions and summons, for Io has nothing to deal with multiple enemies at once outside from Spirits's weak area-of-effect: Beastmaster, Broodmother, Chaos Knight, Lycan, Naga Siren, Nature's Prophet, Phantom Lancer, Shadow Shaman, Terrorblade, Visage, Warlock, Wraith King.
Warlock
* Chaotic Offering can stop heroes who like to use spell immunity and teleport scrolls to safely farm during the early to mid game, since it stuns and also goes through spell immunity. Notable examples: 
Juggernaut, 
Lifestealer.
Warlock
* Supports with useful teamfight or contribution spells will be helpless against Doom: Dazzle, 
Oracle, Warlock.
Additional:
* 
Doom will not only prevent Warlock from casting his abilities in team fights, but also it reduces the healing from Shadow Word.
* 
Devour allows Doom to acquire a stun from neutral creeps, allowing him to interrupt Upheaval without having to use Doom.
Viper
* 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.
Warlock
* 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.
Viper
* 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.
Warlock
* Heroes that have small health pools and little to no escape mechanisms are even easier prey for Necrophos. Ghost Shroud's slow will allow him to catch him with them, and get nuked down with his abilities, even preventing retaliation due to Reaper's Scythe's stun. Such heroes include Crystal Maiden, Witch Doctor, Warlock or Shadow Fiend.
Viper
* 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.
Warlock
* Because all of Warlock's abilities are active abilities, silences can make his impact in fights minimal. Be cautious of heroes that carry silences like Death Prophet, Puck, and the aforementioned Silencer.
Viper
* 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
Warlock
* 
Ursa can shred Warlock's Golems in a few seconds with 
Fury Swipes and 
Overpower.
Viper
* Viper Strike is a strong and breaks Fury Swipes, undispellable slow, making it much easier to kite Ursa for everyone.
Viper
* Viper cannot interrupt heroes with powerful channeling abilities: Bane, Enigma, Shadow Shaman, Warlock
Warlock
* Chaotic Offering's spell immunity piercing stun can stop Black Hole's channeling. Due to this ability's large area of effect, it can be cast at a safe distance from the Black Hole. It also goes through Black King Bar and ignores 
Linken's Sphere.
* Fatal Bonds and Aghanim's Shard upgraded Shadow Word can be used to make Enigma's Eidolons easier to kill, potentially feeding the enemy team. Also,their constant damage will put Blink Dagger on cooldown, potentially forcing Enigma to prematurely activate Black King Bar.
Additional:
* Chaotic Offering pierces spell immunity and is an area of effect ability, therefore it doesn't matter if Enigma buys Black King Bar or Linken's Sphere, Warlock will always be able to cancel the channeling of 
Black Hole.
* Enemies often get clumped up around Black Hole to hit your allies, giving you a perfect opportunity to cast Fatal Bonds, Chaotic Offering, and Upheaval on multiple enemies.
Viper
* Heroes that can drain mana negatively affect Viper's ability to use Poison Attack, Nethertoxin and Viper Strike: Lion, Anti-Mage
Warlock
* While heroes with strong mobility are able to get close or flee from Upheaval, heroes with no escaping abilities or that lack long disables will perish against Warlock. Once the Warlock Golem lands with its stun, its hardly possible to escape when he casts Upheaval. Notable examples: Huskar, Drow Ranger, Lion, Elder Titan, etc.
Warlock
* 
Impale and 
Spiked Carapace interrupts Upheaval with ease.
* Warlock's low health pool, mobility, and high intelligence gain makes him a prime target for Nyx Assassin's burst damage.
Viper
* 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.
Viper
* 
Ice Wall and 
Ghost Walk can be used to kite and escape from Viper.
* 
Chaos Meteor and 
Sun Strike deal heavy damage and can quickly bring Viper down.
* 
Cold Snap, 
Tornado, and 
Deafening Blast are powerful disables that reduce Viper's effectiveness.
* 
E.M.P. burns Viper's limited mana pool, reducing his potential poison damage.
* 
Forge Spirits can melt Viper's armor and reduce his durability.
Viper
* 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.
Warlock
* 
Ice Blast cancels Warlock's Golem's and Shadow Word's healing.
* 
Cold Feet stuns Warlock if he stands in place, forcing him to stop channeling Upheaval immediately or be forced to stop channeling it by it's stun.
Viper
* 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.
Warlock
* Weaver's
Shukuchi allows him to escape from Warlock's Upheaval with high move speed.
Time Lapse allows Weaver to ignore damage from Warlock's Golem and escape.
*
Viper
*
Shukuchi ignores slows and allows Weaver to escape Viper's onslaught.
Time Lapse dispels 
Poison Attack and 
Corrosive Skin and undoes poison damage.
*
* Weaver's high burst damage allows him to kill Viper before being killed.