Slardar
* 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.
Io
* 
Lucent Beam can be used to cancel both, Tether and Relocate.
* Like with Leshrac's 
Diabolic Edict, 
Lightning Storm and 
Pulse Nova abilities. Luna's 
Moon Glaives and 
Eclipse abilities can make short work of Io and its tethered ally, particularly when upgraded with 
Aghanim's Scepter.
Additional:
* Lucent Beam and 0.25s Eclipse Lucent Ministun talent for Eclipse can be used to cancel both, Tether and Relocate.
* Luna's Moon Glaives and Eclipse abilities can make short work of Io and its tethered ally, particularly when upgraded with Aghanim's Scepter.
Slardar
* 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.
Io
* 
Ensnare and 
Song of the Siren can be used to cancel both, 
Tether and 
Relocate and to close the distance on Io.
* 
Rip Tide combined with illusions from 
Mirror Image often finish off Io before he can save himself with Tether or Relocate.
* 
Spirits's weak area-of-effect makes it a bad tool to deal with Naga Siren's illusions from Mirror Image.
* Once Naga Siren buys Aghanim's Scepter, she can gain access to 
Reel In, which not only allows her to cancel both, Tether and Relocate, but also to pull Io to herself and her team while he is affected with Ensnare, similarly to Batrider's 
Flaming Lasso.
* 
Aghanim's Shard upgraded Song of the Siren can also heal the hero Io and his Tethered targed try to gank.
Additional:
* Ensnare and Song of the Siren can be used to cancel both, Tether and Relocate and to close the distance on Io.
* Rip Tide combined with illusions from Mirror Image often finish off Io before he can save himself.
* Spirit's weak area-of-effect makes it a bad tool to deal with Naga Siren's illusions from Mirror Image.
* Once Naga Siren buys Aghanim's Scepter, she can gain access to Reel In, which not only allows her to cancel both, Tether and Relocate, but also to pull Io to herself and her team while he is affected with Ensnare, similarly to Batrider's Flaming Lasso.
* Aghanim's Shard upgraded Song of the Siren can also heal the hero Io and his tethered targed try to gank.
Slardar
* 
Terrorblade starts out with and gains a lot of armor from his agility growth. His illusions also make it difficult for Slardar to focus down the real Terrorblade.
Io
* Terrorblade can easily take advantage of Io's weak durability with 
Reflection and 
Metamorphosis.
* As Io relies on boosting his and his Tethered target's attack speed with 
Overcharge, Terrorblade can take advantage of this with Reflection, which can damage and slow both, Io and his Tethered target.
* Spirits's weak area-of-effect makes it a bad tool to deal with Terrorblade's illusions from 
Conjure Image and Manta Style.
* Io's damage output is one of the weakest, therefore Terrorblade will have plenty of time to save himself with 
Sunder.
* However, Terrorblade has no way of stopping Io to escape with Tether or to stop both, Io and his Tethered target to escape with Relocate besides 
Terror Wave from Aghanim's Scepter.
Additional:
* Terrorblade can easily take advantage of Io's weak durability with Reflection and Metamorphosis.
* As Io relies on boosting his and his Tethered target's attack speed with Overcharge, Terrorblade can take advantage of this with Reflection, which can damage and slow both, Io and his Tethered target.
* Spirits's weak area-of-effect makes it a bad tool to deal with Terrorblade's illusions from Conjure Image and Manta Style.
* Io's damage output is one of the weakest, therefore Terrorblade will have plenty of time to save himself with Sunder.
* However, Terrorblade has no way of stopping Io to escape with Tether or to stop both, Io and it's Tethered target to escape with Relocate besides Terror Wave from Aghanim's Scepter.
Slardar
* Phantom Lancer's 
Doppelganger has a low cooldown and applies a basic dispel on PL, making it hard to keep Corrosive Haze on him.
* Phantom Lancer usually purchases Manta Style which provides another basic dispel to remove Corrosive Haze with.
* Besides Slithereen Crush, Slardar does not have another way to deal with illusions and has a low mana pool, which allows Phantom Lancer with 
Diffusal Blade to quickly build up illusions while draining Slardar's mana.
* 
Phantom Rush outruns Guardian Sprint, forcing Slardar to Blink away or use Slithereen Crush defensively to avoid being killed.
Io
* 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.
Slardar
* Abaddon can cast 
Aphotic Shield on any of his allies to immediately dispel Corrosive Haze and/or the stun and the slow components of Slithereen Crush.
* All of Slardar's debuffs are also removed if Abaddon's 
Borrowed Time triggers.
Slardar
* 
Fortune's End applies a basic dispel which can be used to dispel Corrosive Haze, or even Slardar's own Guardian Sprint.
* 
False Promise is able to dispel Corrosive Haze and Slithereen Crush stun/slow from any allies Oracle chooses to cast it on.
* 
Fate's Edict can also be cast on Slardar to prevent him from proccing his Bash of the Deep.
Io
* 
Cold Embrace can render the extra attack speed from Overcharge meaningless.
* 
Splinter Blast and 
Winter's Curse are very affective against Io, as it has to stay close to his Tethered target.
Io
* Lich's 
Chain Frost forces Io to either give up providing buff to his ally with Tether or suffer devastating damage with his Tethered ally.
* Lich can easily use 
Sinister Gaze to disable Io from getting away with Tether or Relocate.
Io
* Fireblast is a good tool to interrupt Io during its escapes through Tether.
* Ignite can be one of the few spells with enough total damage to out-trade the sustained healing Io provides for its fellow laner.
* However, picking other supports that focus less on the laning phase is generally a better choice against Io.
Io
* 
Phantom Strike allows Phantom Assassin jump directly to Io.
* 
Coup de Grace can make a short work of Io's low health and armor.
Io
* Io is a hero who needs to be close to it's tethered target to make it effective, and that's where Leshrac gets the advantage thanks to many of his area-of-effect abilities.
* Lightning Storm will usually hit both Io and its tethered target since both will be close enough for the lightning to jump.
* Diabolic Edict and Pulse Nova hit all units near Leshrac, meaning he can do colossal damage to both, Io and its tethered target.
Additional:
* Lightning Storm will usually hit both Io and his Tethered target since both will be close enough for the lightning to jump. It can then be followed up by Split Earth.
* Diabolic Edict and Pulse Nova hit all units near Leshrac, meaning he can do colossal damage to Io and his Tethered target.
Io
* Disruptor can always Glimpse back Io or his target after he Relocated nearby.
* Even better, thanks to the indicator on the ground, you can even preemptively drop Static Storm and Kinetic Field on the spot they will relocate to.
* Thunder Strike and Glimpse are also good tools to bring back an Io that Tethered away in the fog of war.
Additional:
* 
Glimpse directly negates Relocate.
* 
Kinetic Field prevents Io from escaping with Tether.
* 
Static Storm can silence and damage both, Io and it's tethered target. And it can also mute both, Io and it's tethered target when upgraded with Aghanim's Scepter.
Io
* Ice Blast prevents Io from healing an ally with Tether and prevents healing from Overcharge
* Io is a common 
Mekansm builder which is useless if he is affected by Ice Blast.
Additional:
* 
Ice Blast prevents Io from healing the target.
* Ancient Apparition can easily harass Io on lane with 
Chilling Touch due to it's high range and damage. This can get even worse if Ancient Apparition buys Aghanim's Scepter and combines it with items that can give him bonus attack damage and attack speed.
* Chilling Touch combined with 
Ice Vortex makes it nearly impossible for Io to escape from 
Cold Feet. Ice Vortex can also make Io and it's tethered target more vulnerable to Ancient Apparition and his allies's magical damage.
Io
* 
Charge of Darkness can be used to escape or counter-initiate against a Relocate gank.
* 
Greater Bash and 
Nether Strike is devastating due to Io's low armor, and can even knock it away from his Tethered target.
Io
* Jakiro's area-of-effect ability arsenal allows him to affect multiple heroes at once, giving Io difficulties in saving them as he can only heal one hero at a time with Tether.
* 
Ice Path can be used to cancel both, Tether and Relocate.
* Jakiro commonly buys 
Rod of Atos that can be used to cancel Relocate, prevent Io in escaping with Tether and make Io easy target for Ice Path and 
Macropyre.
Additional:
* Jakiro's area-of-effect ability arsenal allows him to affect multiple heroes at once, giving Io difficulties in saving them as he can only heal one hero at a time with Tether.
* Ice Path can be used to cancel both, Tether and Relocate.
* Jakiro commonly buys Rod of Atos that can be used to cancel Relocate, prevent Io in escaping with Tether and make Io easy target for Ice Path and Macropyre.
Slardar
* Slardar has high priority on building moblity items such as 
Blink Dagger rather than tank items. Zeus can easily deal large amount of damage to him if not caught out of position first.
Io
* 
Poison Touch allows Dazzle to harass both, Io and it's tethered target on lane. Aghanim's Shard upgraded Poison Touch can also hex both, Io and it's tethered target, preventing them from escaping with Relocate, and also disarming them, silencing them, muting them and rendering them helpless against Dazzle and his allies.
* Io's damage output is one of the weakest, therefore Dazzle will have plenty of time to save an ally with 
Shallow Grave from gank by Io and it's tethered target.
* 
Shadow Wave will always hit both, Io and it's tethered target if they are near the ally Dazzle uses Shadow Wave on, while healing Dazzle's allies near them. Aghanim's Scepter upgraded Shadow Wave can bounce on both, Io and it's tethered target, causing them both to take damage and to be attacked by Dazzle. And unlike Io who doesn't get healed while using Tether, Shadow Wave will always heal Dazzle no matter on which of his allies he uses it on.
* 
Bad Juju will cause both, Io and it's tethered target to lose armor every time Dazzle casts a spell while strengthening armor of Dazzle's allies.
Additional:
* Poison Touch allows Dazzle to harass both, Io and it's Tethered target on lane. Aghanim's Shard upgraded Poison Touch can also hex both, Io and it's Tethered target, preventing them from escaping with Relocate, and also disarming them, silencing them, muting them and rendering them helpless against Dazzle and his allies.
* Io's damage output is one of the weakest, therefore Dazzle will have plenty of time to save an ally with Shallow Grave from gank by Io and it's Tethered target.
* Shadow Wave will always hit both, Io and it's Tethered target if they are near the ally Dazzle uses Shadow Wave on, while healing Dazzle's allies near them. Aghanim's Scepter upgraded Shadow Wave allows Dazzle Shadow Wave directly on Io and it's Tethered target which can also bounce on both, Io and it's tethered target, causing them both to take damage and to be attacked by Dazzle. And unlike Io who doesn't get healed while using Tether, Shadow Wave will always heal Dazzle no matter on which of his allies he uses it on.
* Bad Juju will cause both, Io and it's tethered target to lose armor every time Dazzle casts a spell while strengthening armor of Dazzle's allies.
Io
* 
Homing Missile can be used to cancel escape attempts with Relocate.
* 
Flak Cannon allows Gyrocopter to attack both, Io and his Tethered target, especially when upgraded with Aghanim's Scepter.
* 
Rocket Barrage and 
Call Down allow Gyrocopter to deal serious damage to both Io and his Tethered target.
Additional:
* Homing Missile can be used to cancel escape attempts with Relocate.
* Flak Cannon allows Gyrocopter to attack both, Io and his Tethered target, especially when upgraded with Aghanim's Scepter.
* Rocket Barrage and Call Down allow Gyrocopter to deal serious damage to both Io and his Tethered target.
Io
* Soulbind can target both Io and its Tethered ally, allowing Grimstroke and his team to target both with single target spells. Should Io try to Relocate, Phantom's Embrace can stop its channel to prevent escape.
Additional:
* Grimstroke can catch Io and his Tethered ally easily with 
Soulbind as Io has a tendency to Tether himself with an ally frequently, which also makes them easier targets for Soulbind.
* Io is highly vulnerable to disables. Hence, Grimstroke's 
Phantom's Embrace is a great ability to hinder Io's potential.
Io
* Batrider's Flaming Lasso can be used to cancel Io's attempts to escape with Relocate and drag him away from his Tethered target. And since Io doesn't like buying 
Linken's Sphere, he will be always vulnerable to Batrider's initiations.
* Io's tendency to stick close to it's Tethered target can make Io and it's target vulnerable to Batrider's harrasing.
* Aghanim's Scepter upgraded Flaming Lasso allows Batrider to catch and drag two heroes at once, not just one. Which can potentially turn Io's Tether against him.
Additional:
* Batrider's Flaming Lasso can be used to cancel Io's attempts to escape with Relocate and drag him away from his Tethered target. And since Io doesn't like buying Linken's Sphere, he will be always vulnerable to Batrider's initiations.
* Io's tendency to stick close to it's Tethered target can make Io and it's target vulnerable to Batrider's harrasing.
* Aghanim's Scepter upgraded Flaming Lasso allows Batrider to catch and drag two heroes at once, not just one. Which can potentially turn Io's Tether against him.
Io
* Heroes with either magical, physical or pure damage burst: 
Bane, 
Ember Spirit, 
Leshrac, 
Lina, Luna, 
Nyx Assassin, 
Phantom Assassin, 
Skywrath Mage, 
Tinker, 
Ursa, 
Void Spirit.
Slardar
* 
Medusa cares less than other heroes about armor reduction, since 
Mana Shield blocks 70% of all damage without taking armor/magic resistance into consideration. This makes 60% of your Corrosive Haze ineffective until Medusa's mana is drained.
Io
* Heroes that are hard to gank: 
Axe, 
Death Prophet, Phantom Lancer, 
Slark, 
Centaur Warrunner, 
Bristleback, Medusa, 
Mars.
Slardar
* Other heroes who has armor and slow debuffs won't allow Medusa to disengage from combat: 
Tidehunter, Bristleback, 
Slardar.
Io
* Heroes that are hard to gank: Axe, Death Prophet, Phantom Lancer, Slark, Centaur Warrunner, Bristleback, Medusa, Mars.
Io
* Heroes with either magical, physical or pure damage burst: Bane, Ember Spirit, Leshrac, Lina, Luna, Nyx Assassin, Phantom Assassin, Skywrath Mage, Tinker, Ursa, Void Spirit.
Io
* 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.
Io
* 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.
Io
* 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.
Slardar
* Enigma can be a perfect counter-initiator with his ultimate. A perfectly timed Black Hole will turn the tide of any initiation, especially from heroes like; 
Spirit Breaker, 
Legion Commander, Axe, 
Puck, and Slardar.
Io
* Heroes with either magical, physical or pure damage burst: Bane, Ember Spirit, Leshrac, Lina, Luna, Nyx Assassin, Phantom Assassin, Skywrath Mage, Tinker, Ursa, Void Spirit.
Io
* Heroes that are hard to gank: Axe, Death Prophet, Phantom Lancer, Slark, Centaur Warrunner, Bristleback, Medusa, Mars.
Io
* Heroes with either magical, physical or pure damage burst: Bane, Ember Spirit, Leshrac, Lina, Luna, Nyx Assassin, Phantom Assassin, Skywrath Mage, Tinker, Ursa, Void Spirit.
Io
* 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.
Io
* Squishy heroes (
Io, 
Crystal Maiden, Lina...), as Earth Spirit can deal tons of damage with Magnetize.
Io
* Heroes with either magical, physical or pure damage burst: Bane, Ember Spirit, Leshrac, Lina, Luna, Nyx Assassin, Phantom Assassin, Skywrath Mage, Tinker, Ursa, Void Spirit.
Io
* Heroes that are hard to gank: Axe, Death Prophet, Phantom Lancer, Slark, Centaur Warrunner, Bristleback, Medusa, Mars.
Slardar
* Tidehunter's 
Kraken Shell dispels Corrosive Haze and Bash of the Deep's stun if enough damage is taken. 
Anchor Smash and Kraken Shell's damage block also reduces Slardar's damage.
Io
* Heroes whose abilities can affect multiple enemies at once: 
Dawnbreaker, Ember Spirit, Lina, Luna, 
Jakiro, Leshrac, 
Invoker, 
Muerta, 
Dazzle.
Io
* Heroes that can easily bypass Io's allies to get to Io: 
Riki, 
Tusk, 
Clinkz, 
Sniper, Slark, Phantom Assassin, Void Spirit, 
Storm Spirit, Ember Spirit, 
Earth Spirit, Spirit Breaker, 
Lifestealer.
Io
* 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.
Io
* 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.
Io
* Heroes that are hard to gank: Axe, Death Prophet, Phantom Lancer, Slark, Centaur Warrunner, Bristleback, Medusa, Mars.
Io
* Heroes that can easily bypass Io's allies to get to Io: Riki, Tusk, Clinkz, Sniper, Slark, Phantom Assassin, Void Spirit, Storm Spirit, Ember Spirit, Earth Spirit, Spirit Breaker, Lifestealer.
Io
* Heroes with the ability to heal allies will not be able to heal heroes affected by 
Doom: 
Chen, Dazzle, Io, 
Oracle, 
Omniknight, 
Witch Doctor, 
Winter Wyvern, 
Abaddon, etc.
Io
* Heroes whose abilities can affect multiple enemies at once: Dawnbreaker, Ember Spirit, Lina, Luna, Jakiro, Leshrac, Invoker, Muerta, Dazzle.
Io
* 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.
Slardar
* 
Corrosive Haze reveals Pudge's location, making it hard for him to use Meat Hook from the fog of war on Slardar's teammates or Slardar himself.
* 
Slithereen Crush interrupts Pudge while he is using Dismember.
* 
Guardian Sprint allows Slardar to avoid Meat Hook.
Additional:
* While Slardar has Guardian Sprint activated, 
Rot cannot slow him and 
Meat Hook is easier to avoid.
* Slithereen Crush allows Slardar to interrupt 
Dismember at close range (when Slardar is not a target).
* Corrosive Haze reveals Pudge's location, making it very difficult for him to land hooks from the fog.
Io
* Tether and Overcharge makes it much harder for Pudge to kill a target with Meat Hook, and Relocate can save the Io's ally while Dismember is being channeled.
Io
* 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.
Slardar
* Heroes who can provide True Sight or semi-reveal enemy heroes as Nature's Prophet is prone to buying 
Shadow Blade: 
Bounty Hunter, Slardar, 
Spectre, 
Zeus, Spirit Breaker.
Io
* Nature's Prophet is extremely easy to gank with Relocate while he's split pushing.
* Tether on a friendly unit can destroy Nature Prophet's trees should he surround himself with 
Sprout as a defense.
Slardar
* Corrosive Haze and 
Bash of the Deep will make short work of Huskar's low armor, even if Slardar is alone.
Slardar
* Slardar deals entirely physical damage. He does not have to worry about Counterspell.
* Slithereen Crush and Bash of the Deep prevent Anti-Mage from using Blink, the latter even if Anti-Mage activates 
Black King Bar.
* Corrosive Haze allows allies to take down Anti-Mage before he has a chance to Blink, and maintains vision over him even if he does Blink away.
Additional:
* Slithereen Crush and Bash of the Deep deals physical damage, bypassing the magic resistance bonus from 
Counterspell
* Corrosize Haze significantly increases the damage dealt against Anti-Mage, and makes it harder for him to flee with 
Blink, although Anti-mage can block its casting with with Counterspell
Slardar
* Shadow Fiend, a normal Shadow Blade builder often relies on its invisibility to escape fights. Corrosive Haze reveals Shadow Fiend and also weakens his already low armor.
Io
* Drow Ranger's lack of escape abilities makes her an easy target for Relocate ganks.
Slardar
* Weaver relies on 
Shukuchi to escape and kite enemy heroes. Slardar's Corrosive Haze lowers armor and reveals Weaver, who is already a very frail target.
* Weaver usually builds Linken's Sphere, Corrosive Haze can be used to pop the spell block, additionally the level 25 undispellable talent will prevent Weaver from removing Corrosive Haze with 
Time Lapse, allowing allied heroes to use their abilities on Weaver.
Additional:
* Corrosive Haze lowers armor and reveals Weaver during Shukuchi, who is already a frail target. In addition, Weaver usually builds Linken's Sphere, and Corrosive Haze can be used to "pop" the spell block. His level 25 talent can also make Corrosive Haze undispellable by Time Lapse, which puts Weaver in an even worse situation.
* Guardian Sprint can dodge Weaver's bugs with the movement speed bonus.
Slardar
* While Slardar has Guardian's Sprint activated, 
Powershot cannot slow him and is easier to avoid.
* Slithereen Crush and Bash of the Deep help Slardar put Windranger in place, even when she uses 
Windrun to escape.
* Corrosive Haze from Slardar is very effective against Windranger's already low armor. This becomes even worse if she has Aghanim's Scepter-upgraded Windrun, because it also reveals her position and allowing his allies to use their abilities on Windranger.
* Note that the invisibility provided by Aghanim's Scepter-upgraded Windrun is not broken upon attacking, casting abilities or using items, so it's vital to cast Corrosive Haze beforehand.
Slardar
* Corrosive Haze followed by Slithereen Crush takes advantage of Alchemist's main weakness, being physical damage before he has the change to improve his surviability with items.
* Bash of the Deep will deal lots of damage during the laning phase.
Io
* 
Duel is very effective against Io due to its low health and armor.
Slardar
* With armor items like 
Solar Crest or 
Assault Cuirass combined with Bash of the Deep, Slardar can easily tank the Duel, If not dueled himself, he can drop Legion Commander's armor during duel and/or buff his teammate and save them, leaving her only the choice of dueling supports which can also be saved with fast Blink into Slithereen Crush.
Io
* Tethered heroes are much harder for Legion Commander to kill in Duels.
* Relocate can cancel Duels and save allies.
Io
* Io can escape from Pit of Malice with Tether or Relocate.
* Relocate can counter Dark Rift's split pushing.
Slardar
* Slardar can attack through Plague Wards and gain Bash of the Deep charges, and 
Templar Assassin can spill 
Psi Blades through Plague Wards too.
Slardar
* Heroes with spells that negate invisibility such as Bounty Hunter, Zeus and Slardar prevent her from saving her allies with Moonlight Shadow.
Slardar
* Heroes who can provide True Sight are always credible threats: Slardar, Bounty Hunter, especially Zeus since his 
Lightning Bolt provides True Sight without the need to detect her beforehand to apply the debuff. So even a late-coming Zeus can easily scout a large area to reveal her, and she cannot purge herself from his sight with the dispel talent.
Slardar
* Slardar can chase Dragon Knight down with Guardian Sprint and stun him with both Slithereen Crush and his passive Bash of the Deep. He can also use Corrosive Haze to whittle Dragon Knight's armor.
Io
* 
Take Aim and 
Assassinate allow Sniper to reach Io even if it stays in the backline.
Slardar
* Slardar can use Guardian Sprint with Blink Dagger or Shadow Blade to get close, and Slithereen Crush will stun Sniper and slow him, making him vulnerable to Slardar's teammates.
* Corrosive Haze lowers Sniper's armor and makes Sniper's Shadow Blade useless, easily killing him with a few attacks.
Io
* Heroes with high mobility can approach Sniper: 
Anti-Mage, Earth Spirit, Io, Nature's Prophet, 
Pangolier, Puck, 
Queen of Pain and most notably Riki.
Slardar
* Slardar's Slithereen Crush allows him to stun Spectre and illusions, and Corrosive Haze prevents her from juking with 
Spectral Dagger.
Slardar
* Crystal Maiden's already low armor and easily interruptible ultimate, 
Freezing Field can make Slardar her worst nightmare. Crystal Maiden also often builds 
Glimmer Cape which is revealed by Corrosive Haze.
Slardar
* Slardar does not do well against multiple targets, as his only way to damage multiple targets is Slithereen Crush.
* Meepo's 
Earthbind will root Slardar, making him unable to chase/escape for the time being. Also, 
Poof's low cooldown and high damage can burst Slardar down rather quickly.
Slardar
* Heroes who can stun multiple units at once: 
Dark Willow, Spirit Breaker, Slardar, Invoker, and Tidehunter.
Io
* Tether helps Io escape from Earthbind even if Meepo has Blink Dagger.
* Io's Spirits can pressure Meepo while laning and will usually hit at least one of his clones.
Io
* Heroes that can easily bypass Io's allies to get to Io: Riki, Tusk, Clinkz, Sniper, Slark, Phantom Assassin, Void Spirit, Storm Spirit, Ember Spirit, Earth Spirit, Spirit Breaker, Lifestealer.
Slardar
* Corrosive Haze works much like 
Track, giving the enemy team vision over Riki. While it doesn't give a movement speed or gold bonus, it instead can melt Riki's armor and Slardar can use Guardian Sprint to catch up to him.
* Slardar's Aghanim's Shard, causes Slithereen Crush to apply Corrosive Haze even if Slardar does not have vision over him.
Additional:
* Corrosive Haze makes Riki completely vulnerable to Slardar and his allies, as Riki has no easy way of dispelling it.
* Slardar's physical damage with Slithereen Crush and Bash of the Deep amplified by Corrosive Haze can easily kill Riki.
Io
* Heroes with either magical, physical or pure damage burst: Bane, Ember Spirit, Leshrac, Lina, Luna, Nyx Assassin, Phantom Assassin, Skywrath Mage, Tinker, Ursa, Void Spirit.
Slardar
* Corrosive Haze hinders Nyx Assassin's ganking attempts with 
Vendetta, as well as reducing his armor and make him very vulnerable due to his low health pool.
* Guardian Sprint allows Slardar to catch up with Nyx Asssassin and finish him off if he has vision over him.
Io
* Heroes with either magical, physical or pure damage burst: Bane, Ember Spirit, Leshrac, Lina, Luna, Nyx Assassin, Phantom Assassin, Skywrath Mage, Tinker, Ursa, Void Spirit.
Slardar
* The brutal physical damage of Slithereen Crush and Bash of the Deep can quickly remove Void Spirit's shield and stun him for a while.
* Corrosive Haze provides vision of Void Spirit while he is running away and Guardian Sprint allows Slardar to quickly close the gap
Io
* Fragile heroes: Bounty Hunter has decent nuking capabilities with Shiruken Toss and Jinada thus making fragile heroes easy picks for ganking. Few examples of such heroes are:Crystal Maiden, 
Pugna, Skywrath Mage, Io, Witch Doctor, etc.
Slardar
* Corrosive Haze provides True Sight on its target, exposing Bounty Hunter's position regardless of Shadow Walk.
* Guardian Sprint gives a very high movement speed bonus, allowing him to chase Bounty Hunter even if Slardar is tracked.
Additional:
* Bounty Hunter's 
Shadow Walk is rendered useless with Corrosive Haze and makes Bounty Hunter an easy target for Slardar and his team.
Io
* Heroes with either magical, physical or pure damage burst: Bane, Ember Spirit, Leshrac, Lina, Luna, Nyx Assassin, Phantom Assassin, Skywrath Mage, Tinker, Ursa, Void Spirit.
Slardar
* Slardar is one of the few meele heroes who can lane against Ursa in the early game, out harassing him with Bash of the Deep, and running away from a bad engagement with Guardian Sprint
* Corrosize Haze can force Ursa to cast 
Enrage defensively instead of offensively
* With Corrosize Haze, Slardar's team can quickly dispatch of Roshan, denying one of Ursa's greatest advantages
Io
* 
Quill Spray is very effective against Io, as it has very low armor and has to stay close to the fight to not break its Tether.
Slardar
* Guardian Sprint allows Slardar to outrun Bristleback, even when slowed by Viscous Nasal Goo.
* Corrosive Haze's armor reduction makes Bristleback much less tanky.
Io
* Heroes whose abilities can affect multiple enemies at once: Dawnbreaker, Ember Spirit, Lina, Luna, Jakiro, Leshrac, Invoker, Muerta, Dazzle.
Slardar
* Bounty Hunter and Slardar both have ultimates (Corrosive Haze and Track) that reveal Invoker through Ghost Walk.
Io
* Heroes that can easily bypass Io's allies to get to Io: Riki, Tusk, Clinkz, Sniper, Slark, Phantom Assassin, Void Spirit, Storm Spirit, Ember Spirit, Earth Spirit, Spirit Breaker, Lifestealer.
Slardar
* Slardar's level 25 talent makes Corrosive Haze undispellable, thus providing his allies vision of Slark.
Slardar
* 
Fire Spirits greatly reduces Slardar's already low starting attack speed (which Bash of the Deep relies on), making the laning phase very hard for him and discouraging Slardar from aggressively threatening lane kills.
* 
Supernova, ignoring Phoenix's lack of armor and Slardar's high damage single hits, is extremely hard for Slardar to take down on his own, especially after being hit by Fire Spirits.
* 
Icarus Dive is one of the longest distance escape spells in the game, and can help a good Phoenix escape from Slardar before he gets a Blink Dagger. However, the high cooldown means Phoenix is vulnerable to backstabs from any roamers after said spell is used.
* Slardar can interrupt an Icarus Dive from completing the flight with both of his stuns, however, likely leading to death if Supernova is on cooldown.
* A lot of the items a Phoenix builds throughout the game naturally counter Slardar. 
Shiva's Guard, 
Heaven's Halberd and 
Eul's Scepter of Divinity all stall Slardar's normal attacks in some way, while 
Spirit Vessel's percentage-based damage is good against his innate durability.
Io
* Phoenix's limit AoE, damage-over-time abilities give Io plenty of time to save allies with Relocate.
Slardar
* 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.
Io
* Heroes with abilities that can save teammates are also effective such as 
Shadow Demon, Dazzle, Oracle, Bane, Pugna, Tusk, Winter Wyvern, Io, 
Underlord, 
Treant Protector and 
Keeper of the Light.
Io
* 
Strafe, 
Tar Bomb and 
Burning Barrage from Aghanim's Shard allow Clinkz to quickly kill Io due to its low armor.
* Clinkz iz a hero that very often goes for 
Orchid Malevolence, and its upgrade 
Bloodthorn. Alternatively, Clinkz also loves to buy 
Gleipnir. And if Clinkz has both of them, he will be able to root and silence Io and prevent him from escaping with either Tether or Relocate.
Slardar
* Slardar can reveal Clinkz with Corrosive Haze and make him easy to kill, and his Bash of the Deep also hits hard against Clinkz's naturally low health pool.
* Slardar's Guardian Sprint can catch up with Clinkz's Skeleton Walk.
* The stun and slow from Slardar's Slithereen Crush can hold Clinkz in place.
Additional:
* Clinkz survivability depends entirely on 
Skeleton Walk. Corrosive Haze not only makes its invisibility useless, but also makes Clinkz even more vulnerable to physical damage.
Io
* Heroes that can easily bypass Io's allies to get to Io: Riki, Tusk, Clinkz, Sniper, Slark, Phantom Assassin, Void Spirit, Storm Spirit, Ember Spirit, Earth Spirit, Spirit Breaker, Lifestealer.
Slardar
* Heroes with high physical damage can damage Lifestealer more than he can heal: Bristleback, Clinkz, Luna,
Shadow Fiend, Slardar, Terrorblade
Io
* 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.
Slardar
* Heroes with armor reducing abilities greatly hinder Visage's defense like Slardar and Dazzle.
Io
* 
Living Armor and 
Leech Seed can be used to save a hero from a Relocate gank.
* 
Overgrowth can be used to cancel escape attempts with Relocate.
* Once Treant Protector buys Aghanim's Scepter, he will gain access to 
Eyes in the Forest, that will allow him to enchant a tree which will grant him unobstructed vision in that location, allowing him to keep his allies alerted on Io and his Tethered's attempts to gank them, and which can also allow Overgrowth to damage them and root them if they are within a 800 radius of an tree affected by Eyes in the Forest.
Slardar
* Corrosive Haze will reveal Treant Protector even when he is under the effects of Nature's Guise.
Slardar
*
Bloodseeker's 
Rupture forces Slardar to stay still during fights, preventing Slardar from using Guardian sprint to move in and out of fights. This takes away the ability to initiate and re-initiate with Slithereen Crush's low cooldown. Due to the increased move speed from Guardian Sprint, Slardar can lose health at about 160% the rate of normal heroes while under 
Rupture. Bloodseeker's 
Thirst also gives him enough move speed so that he's one of the few heroes who can outrun or catch up to a Slardar during Guardian Sprint.
Io
*
Thirst allows Bloodseeker to see where Io relocated to, should either Io or the tethered hero have low health.
Rupture forces Io to stay in place, preventing it from using the Tether bonus movement speed to escape.
*