Alchemist
* Alchemist likes to farm fast and be ahead, unfortunately Lone Druid likes to do the same by taking towers.
* 
Acid Spray will never prove a threat to Lone Druid or his Spirit Bear.
* 
Chemical Rage may not prove so useful once Lone Druid procs entangled keeping him in place.
* 
Monkey King Bar is a very good choice on Lone Druid's Spirit Bear and it directly counters any potential 
Radiance from Alchemist.
* 
Assault Cuirass is another very good Spirit Bear item that further makes Alchemist vulnerable to physical damage, which is all Lone Druid does.
* Alchemist is not the kind of hero who wants to go on single target summon units, by the time he has killed the Spirit Bear his teammates might had already been slayed by his teammates. Not to mention Lone Druid can just resummon it, even if he is successful.
Shadow Demon
* 
Chaos Knight, 
Lone Druid, 
Meepo and 
Arc Warden can be hard targets since Shadow Demon's spells are ill-suited to fight many enemies at once.
Alchemist
* 
Pugna's 
Decrepify makes sure that either Alchemist is unable to hit anyone while also being slowed and susceptible to magical damage, or can protect an ally from physical attacks. Besides, Pugna can push early on, when Alchemist is not strong enough to repel it, so by the time Alchemist comes online, he might be forced to sit in base.
Shadow Demon
* All of Pugna's abilities are active, making Demonic Purge break from 
Aghanim's Scepter useless.
* 
Nether Ward punishes Shadow Demon's constant mana usage from spamming spells, especially Shadow Poison.
* An attempt to save an ally using Disruption can easily become a perfect setup for a 
Nether Blast for the enemy.
* 
Life Drain can be used to heal Pugna or an ally to save them from Shadow Demon's abilities.
* However, it can be cancelled by Disruption unless Pugna buys defensive items.
Alchemist
* Melee heroes that get kited easily have hard times dealing with Puck without any lockdowns, as Puck is one of the most mobile heroes. Heroes like 
Sven, 
Lifestealer, 
Ursa and 
Alchemist may have problems to get to Puck without proper initiation items. They also lack reliable lockdowns, as their disables are easily avoidable for Puck, or are just a soft disable.
Shadow Demon
* All of Puck's abilities are active making Demonic Purge break from Aghanim's Scepter useless.
* Shadow Demon will find a hard time catching a Puck, as he can get away with 
Illusory Orb or even 
Waning Rift;
* Puck can dodge Shadow Poison waves and potentially avoid the damage from Demonic Purge with 
Phase Shift. Furthermore, after Disruption ended, Puck can use Phase Shift to avoid any further danger and can blink away with 
Blink Dagger.
* Waning Rift can be used to initiate Shadow Demon, prevent him from using any spells.
Shadow Demon
* 
Dragon Slave will make quick work of the spawned illusions from Disruption.
* An attempt to save an ally using Disruption can easily become a perfect setup for a 
Light Strike Array for the enemy.
* Shadow Demon doesn't have the burst damage to take Lina out of the fight quickly, although Demonic Purge can help his allies kill a squishy Lina.
Shadow Demon
* Poof will destroy Shadow Demon's illusions created by 
Disruption and quickly escapes from 
Shadow Poison & 
Demonic Purge.
Shadow Demon
* Shadow Demon's main source of damage is his low cooldown, high damage spells - meaning Last Word and Global Silence will pretty much take him out of the game for the duration.
* Shadow Demon likes to spam his abilities, which makes him vulnerable to Arcane Curse.
* If Shadow Demon dies near Silencer, he will lose intelligence, reducing his mana pool, mana regen, and attack damage. Furthermore, if the game is long and Shadow Demon dies often, the intelligence losses will also reduce his spell damage.
Alchemist
* 
Ice Blast cancels out Chemical Rage's rapid health regeneration. It can also take advantage of Alchemist's 
Armlet of Mordiggian toggling, as it will make HP drain insanely fast, essentially killing the bearer in no time.
Additional:
* Ice Blast nullifies the health regeneration granted by Chemical Rage, which Alchemist greatly relies on to stay alive in battle.
* Alchemist tends to build Armlet of Mordiggian which can be deadly during Ice Blast.
Shadow Demon
* Shadow Demon's Demonic Purge with Aghanim's Scepter cannot break 
Reincarnation, which could put him in a disadvantage against Wraith King if his whole team is with him.
* 
Vampiric Spirit can out-heal the damage from Shadow Demon's abilities.
* However, Wraith King is a single-target hero, so he cannot deal with Disruption illusions.
Shadow Demon
* Diabolic Edict and Pulse Nova will tear apart any illusions spawned from Disruption
* Split Earth can punish improper usage of Disruption.
* Leshrac does not have any buffs that can be removed by Demonic Purge.
Additional:
* 
Pulse Nova makes quick work of any illusions with amplified damage, and deals damage even if Leshrac is in Disruption.
* An attempt to save an ally using Disruption can easily become a perfect setup for a 
Split Earth for the enemy.
* Disruption does not stop 
Diabolic Edict and Pulse Nova once they start pulsing, and even worse it provides a safe shelter for Leshrac to keep pumping up his powerful AoE damage onto the battlefield.
* Shadow Demon doesn't have the burst damage to take Leshrac out of the fight quickly, although Demonic Purge can help his allies kill a squishy Leshrac.
Alchemist
* Alchemist's reliance on fast attack speed to do single-target damage makes him vulnerable to 
Static Link. It also goes through 
Black King Bar, which is a standard item on Alchemist.
* 
Eye of the Storm is great against high health strength heroes as it reduces their survivability to physical damage.
* Razor has early lane push to counter Acid Spray.
Alchemist
* 
Quas-
Exort Invoker can win the mid lane easily against Alchemist because Quas regeneration will nullify Acid Spray's damage over time and Exort damage bonus will allow Invoker to out last hit Alchemist.
Shadow Demon
* 
Death Ward with Aghanim's Scepter makes quick work of the spawned illusions from Disruption.
* However, it can be cancelled by Disruption until Witch Doctor buys 
Linken's Sphere or Black King Bar.
* All of Witch Doctor's abilities are active, making Demonic Purge break from Aghanim's Scepter useless.
* 
Voodoo Restoration can out-heal the damage from Shadow Demon's abilities.
* An attempt to save an ally using Disruption can easily become a perfect setup for a 
Maledict or 
Paralyzing Cask for the enemy.
Shadow Demon
* Shadow Demon will have a hard time catching Storm Spirit, as he can get away with 
Ball Lightning.
* 
Static Remnant will make quick work of the spawned illusions from Disruption.
* With very high mobility and usually being paired with 
Orchid Malevolence, he can catch Shadow Demon with ease both in ganks and in teamfights if Shadow Demon has no survivability items.
Alchemist
* 
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.
Shadow Demon
* All of Lion's abilities are active making Demonic Purge break from Aghanim's Scepter useless.
* 
Hex and 
Mana Drain can make quick work of whatever illusions you're creating, especially when he acquires his Talents at level 20 and 25.
* An attempt to save an ally using Disruption can easily become a perfect setup for a 
Earth Spike or 
Finger of Death with Aghanim's Scepter for the enemy.
Alchemist
* Skywrath Mage can easily harass Alchemist in the laning phase with multiple Arcane Bolts. Additionally, if Alchemist is in the process of throwing an 
Unstable Concoction, and has no way to dispel Ancient Seal, the self stun becomes an easy set up for Mystic Flare.
* Caution, however, as a decently farmed Alchemist with {Item ID:Radiance} and {Item ID:Manta Style} can easily send illusions to harass and force Skywrath Mage out.
Shadow Demon
* All of Queen of Pain's abilities are active, making Demonic Purge break from Aghanim's Scepter useless.
* However, Demonic Purge can help his allies kill a squishy Queen of Pain.
* 
Blink allows Queen of Pain to escape from Shadow Demon's abilities if he doesn't have disables.
* An attempt to save an ally using Disruption can easily become a perfect setup for a 
Sonic Wave for the enemy.
Alchemist
* Visage can quickly kill heroes with low to medium base armor and no innate escape mechanism. Examples include Alchemist, 
Crystal Maiden and 
Zeus.
Alchemist
* 
Clinkz can use 
Burning Army in teamfights which will cause a problem for Alchemist.
Alchemist
* 
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.
Shadow Demon
* 
Lycan and 
Weaver has abilities that allow them to move at maximum movement speed, and those abilities can't be dispelled, potentially wasting the slow from Demonic Purge.
Shadow Demon
* You can potentially kill a fragile Weaver by using Disruption during 
Shukuchi with a well-placed 
Sentry Ward, wasting the Shukuchi. But odds are he'll wait to get low health, 
Time Lapse the damage away and Shukuchi away once more.
Shadow Demon
* Chaos Knight, Lone Druid, Meepo and Arc Warden can be hard targets since Shadow Demon's spells are ill-suited to fight many enemies at once.
Alchemist
* Heroes who rely on burst physical damage are affected by Lucky Shot's disarm: 
Terrorblade, Sven, Clinkz, 
Windranger, Alchemist, 
Dragon Knight, 
Legion Commander
Alchemist
* Heroes who rely on physical damage output to be effective will fare badly against Muerta's 
Pierce the Veil: 
Phantom Assassin, Terrorblade, 
Drow Ranger, Lifestealer, 
Anti-Mage, Alchemist, Lycan, Clinkz, 
Sniper.
Alchemist
* 
Feast is good against high health strength heroes such as Alchemist.
* 
Rage allows Lifestealer to not be targetable by Unstable Concoction, possibly making Alchemist stun himself.
* Since Lifestealer build Aghanim's Scepter upgrades 
Infest similliar 
Heaven's Halberd can applies an undispellable disarm so Alchemist cannot attack during Chemical Rage, forcing him to activate Black King Bar beforehand.
Shadow Demon
* Melee carries such as Sven, Ursa or Lifestealer can be slowed and easily kited with Demonic Purge.
Alchemist
* Chemical Rage will rarely save Alchemist against Ursa's 
Fury Swipes.
* 
Enrage allows Ursa to both be a threat to Alchemist and avoid his over time damage.
Shadow Demon
* Melee carries such as Sven, Ursa or Lifestealer can be slowed and easily kited with Demonic Purge.
Additional:
* Shadow Demon's Demonic Purge renders Ursa useless even through Black King Bar as it slows him, continually purges his Overpower charges and can not be dispelled by Ursa's Enrage.
* Disruption is a good way to save teammates against Ursa. Disrupting Ursa is also a good way to kite him, as it can not be dispelled by Enrage.
Alchemist
* 
Tidebringer will deal lots of damage to Alchemist before he builds physical survivability items.
* 
Torrent and 
X Marks the Spot can control Alchemist at all stages of the game before he has Black King Bar.
* 
Ghostship's rum buff will greatly reduce the Alchemist's damage output in teamfights including his Radiance.
Shadow Demon
* Similarly, they can negate your X Marks The Spot & Torrent combo by protecting your target when you use Return. Good candidates to negate your combo include 
Outworld Destroyer and his 
Astral Imprisonment, and 
Shadow Demon and his Disruption.
* Heroes with hide abilities can often dodge a Ghostship just before it hits.
* Similarly, they can negate your X Marks The Spot & Torrent combo by protecting your target when you use Return. Good candidates to negate your combo include Outworld Destroyer and his Astral Imprisonment, and Shadow Demon and his Disruption.
* A 
Eul's Scepter of Divinity can also do the trick, but, unlike the previously mentioned abilities, you can only use it on yourself and not your allies.
Alchemist
* 
Shadow Dance allows Slark to not be targeted by Unstable Concoction, making Alchemist stun himself and making himself vulnerable to the enemy.
* 
Dark Pact also allows him to just purge off the stun if timed correctly.
* 
Essence Shift will steal stats over long durations at a time should Alchemist lack the damage to kill Slark.
Shadow Demon
* Heroes that lose a great amount of damage output and become less threatening: Phantom Assassin, Sven, 
Slark, 
Phantom Lancer.
* Once you have an Aghanim's Scepter, Shadow Demon instantly reaches a new power spike and becomes a counter for a variety of heroes that have strong passives.
* Heroes that lose a great amount of their tankiness and become easier to finish off: 
Bristleback, 
Spectre, Phantom Assassin, 
Enchantress, Dragon Knight.
* Heroes that lose a great amount of damage output and become less threatening: Phantom Assassin, Sven, Slark, Phantom Lancer.
* You can always stack camps and farm the scepter with Shadow Poison.
Alchemist
* Alchemist has very bad armor and does not build armor items for the large majority of his build, so Jingu Mastery and Wukong's Command can be very deadly.
* 
Desolator, 
Sange and Yasha or 
Diffusal Blade can all be purchased to increase your damage against Alchemist or just to keep your movement speed high enough to match him while Chemical Rage is active.
* Monkey King is an agility hero and scales with armor, so Acid Spray loses it's effectiveness later in the game.
Alchemist
* Heroes with wide AoE abilities will reveal Monkey King through Mischief: 
Necrophos, 
Phoenix, Alchemist, 
Earthshaker, 
Razor, 
Tinker, 
Leshrac, 
Queen of Pain
Alchemist
* 
Untouchable greatly reduces Chemical Rage's attack speed advantage.
Shadow Demon
* Heroes with break can disable Untouchable for a while: 
Doom and Shadow Demon (via Aghanim's Scepter), Viper, 
Shadow Shaman with Hex Breaks talent.
Alchemist
* Heroes who are melee but cannot fight back against Eclipse will really struggle with Luna: 
Monkey King, Alchemist, 
Timbersaw.
Shadow Demon
* Illusions and summons are double-edge sword type of matchup for Luna. On one hand, they can tank damage from Eclipse, but on the other hand, she can easily clear them before Eclipse with Moon Glaives. Examples include Spectre, Shadow Demon, Phantom Lancer, 
Naga Siren, Chaos Knight, Terrorblade) or bring other units into the fight (such as 
Nature's Prophet, Lone Druid, 
Chen, Enchantress, Meepo and Arc Warden).
Shadow Demon
* Demonic Purge takes off Luna's superior mobility, removing the need for chasing her and allowing your team to reposition in team fights or escape when at low HP. If Shadow Demon has Aghanim's Scepter it will also take away glaive bounces and extra damage from Luna's passive. And Luna's commonly items Manta Style and Black King Bar does not work dispell to Demonic Purge
* Luna's illusions created by Disruption are very valuable with their 
Moon Glaives. These will effectively counter her pushing attempts and are painfully effective in team fights.
* Disruption can be used to save an ally from 
Eclipse.
* For the same reasons, Shadow Demon makes a very powerful ally for Luna when they are in the same team.
Additional:
* Demonic Purge takes off Luna's superior mobility, removing the need for chasing her and allowing your team to reposition in team fights or escape when at low HP. If Shadow Demon has Aghanim's Sceptre it will also take away glaive bounces and extra damage from Luna's passive.
* Luna's illusions created by Disruption are very valuable with their Moon Glaives. These will effectively counter her pushing attempts and are painfully effective in team fights.
* Disruption can be used to save an ally from Eclipse.
* For the same reasons, Shadow Demon is a very good ally for Luna when they are in the same team.
Alchemist
* Chemical Rage mitigates damage from 
Burning Spear.
Additional:
* Chemical Rage negates almost all damage from Burning Spears.
Shadow Demon
* Shadow Demon's Shadow Poison can quickly stack to the point where Huskars generally low health is easily finished off.
* Shadow Demon's Disruption can turn Huskar's high attack speed and regeneration against him, It also makes him an easy target for Shadow Poison,
* Shadow Demon commonly builds a 
Meteor Hammer, allowing him to land a heavy stun on Huskar
* Shadow Demon's upgraded Demonic Purge breaks Huskar, It also pierces Spell Immunity, Without his passive for 7 seconds Huskar quickly falls in battle
* However note that Shadow Demon is a squishy target and you can often overwhelm him if he is alone, But he can still Disrupt you to escape
Additional:
* Shadow Poison can quickly stack up on Huskar, And with his naturally low health you don't need as many stacks to be effective.
* Disruption turns Huskars high attack speed against him, They also have the highest survivability as illusions due to his passive 
Berserker's Blood, It also allows you to put Shadow Poison stacks on him,
* Dissimulate turns Huskar's burning damage against his team, You can cast it on an ally who is taking a bunch of Burning Spear stacks and cause Huskar to take high amounts of damage as well
* Scepter upgraded Demonic Purge is your most effective weapon against him, It's 7 second Break causes him to quickly die in battle
Alchemist
* Heroes that can cancel Charge of Darkness: 
Ogre Magi, Earthshaker, 
Lion, 
Rubick, 
Lina, 
Luna, 
Jakiro, 
Dawnbreaker, Alchemist, Ogre Magi, 
Axe, Shadow Shaman, Naga Siren, 
Mars, 
Bane, 
Pudge, 
Clockwerk.
Shadow Demon
* Heroes with ways to protect themselves or allies from Spirit Breaker's initiation: Shadow Demon, Outworld Destroyer, 
Omniknight, Dawnbreaker.
Shadow Demon
* Shadow Demon can waste precious seconds of 
Windrun with Disruption.
* Alternatively, Demonic Purge can be used to dispel it altogether, leaving her completely defenseless for 7 seconds.
* Disruption can be used to save an ally if they get stunned by 
Shackleshot.
Additional:
* Shadow Demon can waste precious seconds of Windrun with Disruption.
* Alternatively, Demonic Purge. can be used to dispel it altogether, leaving her completely defenseless.
* Disruption can be used to save an ally if they get stunned by Shackleshot.
Shadow Demon
* Shadow Demon's spammable illusions can be used to scout Techies' 
Proximity Mines.
Shadow Demon
* Disruption can banish Faceless Void or an ally in Chronosphere, making it a less effective ability.
* Faceless Void's illusions created by Disruption will not get stunned by Chronosphere, allowing Shadow Demon to attack Faceless Void in his Chronosphere.
* Casting Disruption after releasing Shadow Poison charges will make Time Walk unable to backtrack the damage.
* Shadow Poison is a good way to deal damage as the initial damage and the release damage can't both be Time Walked at the same time.
* Demonic Purge is a great slow, useful to force out a Time Walk early and can break Time Lock with Aghanim's Scepter.
Alchemist
* Alchemist's Acid Spray can heavily damage Chen's creeps and disrupt his jungling.
* Alchemist builds items like Radiance and 
Battle Fury, allowing him to quickly clear Chen's creeps.
* Alchemist's Greevil's Greed will grant him more bonus gold as he kills Chen's creeps.
Shadow Demon
* In the laning stage, making illusions of Venomancer will turn his 
Poison Sting back at him, making for an easy gank at level one, and for later when your mid comes for ganks.
Shadow Demon
* Disruption instantly removes Phantom Embrace, and can potentially save allies affected by Soulbind.
* Demonic Purge dispels Ink Swell.
Shadow Demon
* Disruption sets up Anti-Mage for a chain disable. The illusions will deal extra damage due to Mana Break.
* Shadow Poison hits Anti-Mage even after he's Blinked away.
* If Shadow Demon has Aghanim's Scepter, Demonic Purge can break Mana Break and Counterspell, weakening both his offense and defense.
Additional:
* While it is unwise to encounter Anti-Mage alone, Disruption's considerable cast range can become a perfect setup for any hard-disable to follow up. If he is pinned down, Anti-Mage will quickly face his demise when the illusions deplete his already low mana pool. 
Manta Style will easily allow him to escape, however.
* The illusions can be controlled to quickly sap mana from any other target, making Anti-Mage one of the most valuable targets to disrupt.
Alchemist
* Magnus has very mediocre damage against Alchemist, because he can survive the stun duration of Reverse Polarity with Chemical Rage.
Shadow Demon
* The constant dispel from Demonic Purge will make any attempt to save the victim or himself by 
Surge become futile. For what it's worth, Demonic Purge will also dispel 
Ion Shell.
Alchemist
* Chemical Rage will take down 
Tombstone in no time.
Additional:
* With Greevil's Greed, Alchemist can farm Tombstone zombies and gain a significant gold advantage.
Shadow Demon
* Her illusions with 
Desolate are very valuable, especially when they are usually paired with Radiance. Unlike blink or force movement, 
Spectral Dagger's escaping mechanic requires manual movement, and therefore Demonic Purge can hold her back really hard and allow your allies to finish her off.
* If she tries to kill you or any key ally with 
Haunt at any point of the game, remember to not panic and always use Disruption on the illusion, whether it is fake or the real Spectre herself. When the situation calls, Demonic Purge can save a second victim from a haunting Spectre.
* When upgraded by Aghanim's Scepter, Demonic Purge can remove Spectre from a fight by disabling Desolate and 
Dispersion, negating her damage and tankiness respectively.
Shadow Demon
* Shadow Demon's Disruption will allow his allies to maneuver around you. It can also be used to protect an ally from your abilities, or Astral Imprisonment - Meteor Hammer combo.
* 
Disseminate turns your high damage Arcane Orb and Sanitiy's Eclipse against you and your teammates.
* Scepter upgraded Demonic Purge will break your Essence Flux passive for 7 seconds, preventing you from regaining mana, and severely hindering your damage output.
Alchemist
* Alchemist can easily farm Spiderlings with Acid Spray and Greevil's Greed.
* Alchemist's Chemical Rage nullifies Broodmother's 
Insatiable Hunger
Additional:
* Greevil's Greed makes Broodmother’s spiderlings far more valuable to Alchemist making it important that he does farm them as opposed to other heroes where the spider's bounties are negligible.
* Acid Spray makes it difficult to attack Alchemist in lane without losing some spiderlings to the damage over time, potentially giving him farm he wouldn't have otherwise.
Shadow Demon
* Disruption can protect Shadow Demon's allies from Fortune's End, preserving healing or buffs. It can also catch Oracle's allies, allowing Shadow Poison to be used without being dispelled.
* Demonic Purge prevents over-time healing during False Promise, such as Purifying Flames and 
Urn of Shadows. If he has Aghanim's Scepter, this issue can persist for longer or on multiple allies.
* It will not, however, prevent healing from instant abilities, items, or auras, making 
Mekansm a good choice against him.
Shadow Demon
* Shadow Demon with an Aghanim's Scepter will use Demonic Purge to disable Curse of Avernus and the passive component of Borrowed Time. If this is combined with a silence, Borrowed Time will not trigger at all.
* Even without Aghanim's Scepter, he can still waste Borrowed Time with Disruption. Curse of Avernus fully works on illusions, turning the passive ability against him.
Shadow Demon
* Heroes with summons or illusions makes Sacred Arrow harder to land: Shadow Demon, Phantom Lancer, Nature's Prophet.
Shadow Demon
* Although Phantom Lancer will generate strong illusions, and you can also break his 
Juxtapose with an Aghanim's Demonic Purge, you have a small chance of guessing which is the real Phantom Lancer after he uses 
Doppelganger.
Alchemist
* Heroes that require burst damage to kill will be difficult for Phantom Lancer to take down: Timbersaw, Axe, Bristleback, Alchemist and 
Underlord
Shadow Demon
* Shadow Demon's Demonic Purge is undispellable.
* Heroes with undispellable debuffs will help identify the real Phantom Lancer through visual effects or debuff indicators, provided that it was cast on the real Phantom Lancer to begin with:
* Doom's 
Doom marks Phantom Lancer with a highly visible effect, and also silences and mutes him.
* 
Bloodseeker's 
Rupture shows a clear red trail effect on the real Phantom Lancer.
* 
Ancient Apparition's Ice Blast will only debuff Phantom Lancer and not his illusions.
* 
Grimstroke's 
Soulbind is undispellable.
* Shadow Demon's Demonic Purge is undispellable.
* Monkey King's 
Jingu Mastery is undispellable and puts a big yellow Mark over his head.
Additional:
* Phantom Lancer's strength is the sheer amount of illusions he can conjure, Dissimulate can be cast on an ally that he is focusing to quickly thin out his ranks
* Landing a upgraded Demonic Purge on the real Phantom Lancer prevents him from making very many illusions (His only source being Doppelganger), You can reapply as needed if you have the Shard
* Disrupting Phantom Lancer allows you to create multiple extra illusions with Juxtapose, As he is a common carrier of Diffusal Blade, you can also drain the mana of any nearby heros
Shadow Demon
* Primal Beast really suffers against supports he cannot bully in the lane: this includes 
Dazzle, Shadow Demon and 
Dark Willow since they can use their respective abilities to stop Primal Beast from dealing burst damage, or make it hard for him to stay in range.
Shadow Demon
* Heroes with high physical damage output but lack of reliable escape mechanisms are always a good target for a solo gank: Sniper, 
Shadow Fiend, 
Troll Warlord, Drow Ranger. Those heroes, however, are dangerous if they manage to close the gap, so take caution.
Shadow Demon
* Heroes with high physical damage output but lack of reliable escape mechanisms are always a good target for a solo gank: Sniper, Shadow Fiend, Troll Warlord, Drow Ranger. Those heroes, however, are dangerous if they manage to close the gap, so take caution.
Shadow Demon
* Heroes who can summon illusions and summons because Terrorblade has no abilities to deal with multiple enemies at once outside Reflection: Shadow Shaman, Naga Siren, 
Broodmother, Lycan, 
Enigma, Chaos Knight, Phantom Lancer, Shadow Demon, 
Dark Seer, Nature's Prophet, 
Invoker, 
Morphling, 
Visage, Grimstroke with Aghanim's Scepter.
Shadow Demon
* Heroes with break abilities: Shadow Demon (with Aghanim's Scepter), Viper.
Shadow Demon
* Shadow Demon's Demonic Purge with Aghanim's Scepter disables Bristleback's passives.
Shadow Demon
* Heroes with high physical damage output but lack of reliable escape mechanisms are always a good target for a solo gank: Sniper, Shadow Fiend, Troll Warlord, Drow Ranger. Those heroes, however, are dangerous if they manage to close the gap, so take caution.
Shadow Demon
* Heroes that lose a great amount of their tankiness and become easier to finish off: Bristleback, Spectre, Phantom Assassin, Enchantress, Dragon Knight.
* Once you have an Aghanim's Scepter, Shadow Demon instantly reaches a new power spike and becomes a counter for a variety of heroes that have strong passives.
* Heroes that lose a great amount of their tankiness and become easier to finish off: Bristleback, Spectre, Phantom Assassin, Enchantress, Dragon Knight.
* Heroes that lose a great amount of damage output and become less threatening: Phantom Assassin, Sven, Slark, Phantom Lancer.
* You can always stack camps and farm the scepter with Shadow Poison.
Alchemist
* He can quickly take out heroes with low armor (
Tiny) with his great physical damage.
Shadow Demon
* Heroes that can gain vision over trees to catch Tinker: Invoker, Shadow Demon, 
Batrider.
Shadow Demon
* Hex abilities prevent attacking, ability and item usage, which is a severe problem for Phantom Assassin as it prevents her from using Black King Bar, the one item that helps protect her against the aforementioned dangers. Doom and Shadow Demon with Aghanim's Scepter also disables Phantom Assassin's Evasion and Critical Strike, removing much of her damage and survivabaility: Doom, 
Disruptor with Aghanim's Scepter, Dazzle with 
Aghanim's Shard
Shadow Demon
* Heroes that can purge buffs can dispel Guardian Angel: Invoker, Shadow Demon, 
Oracle.
Additional:
* Demonic Purge can dispel 
Guardian Angel on the key target during combat, allow your allies to finish them.
Shadow Demon
* Heroes with hiding abilities can protect disabled allies: Outworld Destroyer, Shadow Demon, 
Tusk, Phoenix with Aghanim's Scepter.
Shadow Demon
* 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.
Additional:
* Be ready to save an ally from 
Omnislash with your Disruption.
* Spawning 
Juggernaut's illusions is a great deal, as his base attack time is low and he has a critical strike. Illusions will benefit from both.
* Demonic Purge will prevent Juggernaut's desperate attempt to flee using 
Blade Fury. However, it cannot stop him if he is using 
Town Portal Scroll.
Shadow Demon
* Heroes with high physical damage output but lack of reliable escape mechanisms are always a good target for a solo gank: Sniper, Shadow Fiend, Troll Warlord, Drow Ranger. Those heroes, however, are dangerous if they manage to close the gap, so take caution.
Shadow Demon
* Heroes who can hide the Dueled target (Outworld Destroyer, Shadow Demon, Tusk, Phoenix with Aghanim's Scepter etc).
Additional:
* Disruption can save allies and mess up an initiation from an enemy Legion Commander. Using Disruption on your ally that is affected by 
Duel will leave her totally exposed without the benefit of the life steal from 
Moment of Courage. A precise decision to Disrupt Legion Commander or her victim is crucial to waste Duel's potential.
* Demonic Purge cannot be dispelled by a hard dispel from 
Press the Attack, which in turn can be dispelled by your ultimate.
Shadow Demon
* Heroes that can punish aggressive heroes, such as: Leshrac, Shadow Demon, Pugna, 
Death Prophet.
Alchemist
* Sprout is good for trapping melee carries with no escape abilities: Sven, Alchemist, Lifestealer etc.
Alchemist
* Acid Spray and Greevil's Greed will quickly destroy pushes with treants.
* Because of his poor movement speed,Alchemist can catch up and kill him with Chemical Rage.
Shadow Demon
* For the same reason, he has to be slightly more cunning when playing against heroes that can scout the treeline, such as Ancient Apparition and his 
Ice Vortex and Shadow Demon and his Shadow Poison.
Shadow Demon
* Shadow Demon, Outworld Destroyer and Tusk can all save a Lasso'd teammate with their defensive spells.
Alchemist
* Heroes who struggle to fight back against Sven at any point in the game are at a severe disadvantage: Alchemist, Anti-Mage, Crystal Maiden.
Shadow Demon
* Heroes that lose a great amount of damage output and become less threatening: Phantom Assassin, Sven, Slark, Phantom Lancer.
* Once you have an Aghanim's Scepter, Shadow Demon instantly reaches a new power spike and becomes a counter for a variety of heroes that have strong passives.
* Heroes that lose a great amount of their tankiness and become easier to finish off: Bristleback, Spectre, Phantom Assassin, Enchantress, Dragon Knight.
* Heroes that lose a great amount of damage output and become less threatening: Phantom Assassin, Sven, Slark, Phantom Lancer.
* You can always stack camps and farm the scepter with Shadow Poison.
Alchemist
* Doom can disable Chemical Rage's increased healing, rendering Alchemist helpless against Doom.
* Attacks from 
Infernal Blade can deal serious damage to Alchemist as it deals damage based on the hero's maximum health.
Alchemist
* Doom's low armor makes him weak against Alchemist's high physical damage output.
Alchemist
* Heroes who are entirely reliant on dealing physical damage and/or have very little to no area-of-effect abilities will make Underlord tickle and will have no effect against him thanks to his 
Atrophy Aura, and will also be unable to ambush Underlord and his team if Underlord chooses to use 
Fiend's Gate to get to a designated point of the map: Phantom Assassin, Terrorblade, Troll Warlord, Drow Ranger, Phantom Lancer, Chaos Knight, Sven, 
Wraith King, 
Bounty Hunter, Alchemist, 
Templar Assassin, 
Nyx Assassin, Bane.
Alchemist
* Heroes with strong area-of-effect damaging and/or disabling abilities will be able to intercept Underlord and his team when they exit from Fiend's Gate: Luna's Aghanim's Scepter upgraded Eclipse, Dawnbreaker's 
Solar Guardian, Axe's 
Berserker's Call, Mars's 
Arena of Blood, Jakiro's 
Macropyre, 
Dual Breath and 
Ice Path, Naga Siren's 
Song of the Siren, Razor's Eye of the Storm and 
Plasma Field, Lina's Light Strike Array, Broodmother's 
Spinner's Snare from Aghanim's Scepter, 
Elder Titan's 
Earth Splitter and 
Echo Stomp, Alchemist's Unstable Concoction and Acid Spray, Queen of Pain's Sonic Wave, Dark Seer's 
Wall of Replica and 
Vacuum, 
Venomancer's 
Noxious Plague and 
Poison Nova from Aghanim's Scepter, Oracle's 
Fortune's End and 
Rain of Destiny from Aghanim's Shard, Bloodseeker's 
Blood Rite, Enigma's 
Black Hole and 
Midnight Pulse, Shadow Fiend's 
Requiem of Souls, Batrider's Aghanim's Scepter upgraded 
Flaming Lasso, 
Firefly, 
Flamebreak and 
Sticky Napalm, Ancient Apparition's Ice Blast, 
Sand King's 
Epicenter, 
Sand Storm and 
Burrowstrike, 
Gyrocopter's 
Call Down, 
Ember Spirit's 
Sleight of Fist, Death Prophet's 
Exorcism and 
Silence, Monkey King's 
Wukong's Command, Crystal Maiden's 
Freezing Field, 
Muerta's 
The Calling, 
Medusa's 
Stone Gaze, Zeus's 
Nimbus from Aghanim's Scepter. Dark Willow's 
Bramble Maze, 
Pangolier's 
Swashbuckle, Grimstroke's Soulbind, 
Ink Swell and 
Stroke of Fate, Earthshaker's 
Echo Slam and 
Fissure, 
Puck's 
Dream Coil and Waning Rift, Winter Wyvern's 
Winter's Curse, 
Magnus's 
Reverse Polarity.
Alchemist
* 
Reaper's Scythe can kill Alchemist before Chemical Rage has the time to heal him.
* 
Ghost Shroud can prevent Alchemist from attacking Necrophos, as well as make him immune to Acid Spray and Unstable Concoction damage.
* 
Heartstopper Aura will do damage as long as Necrophos is alive based on health percentage, which is a problem for a strength hero such as Alchemist.
Shadow Demon
* Disruption can save an ally from a fatal Reaper's Scythe.
* Demonic Purge can remove Ghost Shroud, making Necrophos vulnerable to physical damage and preventing him from regenerating health.
Shadow Demon
* Icarus Dive quickly escapes from Shadow Demon abilities, especially Demonic Purge.
* Phoenix AoE abilities remove Shadow Demon's illusions created by Disruption.
Alchemist
* Chemical Rage kills Phoenix very quickly in 
Supernova.
Alchemist
* 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.
Shadow Demon
* Disruption will save Shadow Demon's teammates from being killed by Counter Helix or Culling Blade.
* Demonic Purge slows Axe to a crawl, making him nearly useless after initiating. If Shadow Demon has Aghanim's Scepter, it will also break Counter Helix.
* 
Demonic Cleanse clears Battle Hunger and Aghanim's Shard Counter Helix Damage Reduction, both allowing targets to escape and reducing your own survivability.
Additional:
* While it is unwise to encounter Axe alone, Disruption can be used to save your allies from Axe's initiate Berserker's Call, or, if timed correctly, from his 
Culling Blade.
* Illusions spawned from Axe has the Counter Helix passive, which with deal some nasty damage if an enemy focuses them
* Your upgraded Demonic Purge breaks Axe's primary damage output: Counter Helix, This can be used on him during Berserker's Call to seriously hinder him.
* Demonic Cleanse will clear 
Battle Hunger, which is Axe's method of catching heroes, and Shard upgraded Counter Helix's Damage Reduction, which is one of Axe's primary survivability abilities.
Shadow Demon
* Chaos Knight, Lone Druid, Meepo and Arc Warden can be hard targets since Shadow Demon's spells are ill-suited to fight many enemies at once.
Shadow Demon
* Heroes with summons or illusions can counter Flux, such as 
Beastmaster , Chen, or Shadow Demon.
Alchemist
* Ember's magic damage build is able to burst down Alchemist due to his low strength gain and Alchemist's normal item pick up.
Shadow Demon
* Disruption is not reliable enough to catch an Ember Spirit with a backup
Fire Remnant.
Sleight of Fist will also make quick work of the spawned illusions.
Flame Guard with your Demonic Purge.
*
* The best you can do against an Ember Spirit is to dispel his