* Kraken Shell dispels both Shadowraze's damage amplification stacks and Requiem of Soul's damage reduction (provided Tidehunter has taken enough damage).
* Ravage cancels Requiem of Souls if Shadow Fiend isn't protected by Black King Bar.
Additional:
* Kraken Shell dispels the damage amplification stacks of Shadowraze as well as the damage reduction from Requiem of Souls (provided he has taken enough damage).
* Anchor Smash reduces Shadow Fiend's large attack damage, Kraken Shell makes Tidehunter the last target Shadow Fiend wants to attack.
* Ravage can easily cancel Requiem of Souls if Shadow Fiend isn't protected by Black King Bar.

* Kraken Shell dispels the stun from Paralyzing Cask. However, it does not dispel the damage from Maledict.
* Once Witch Doctor first uses his Death Ward in team fights, Tidehunter can simply cancel it with Ravage, turning the tables against him, especially if Witch Doctor does not have a Black King Bar.
* As a precaution, Witch Doctor should let Tidehunter use Ravage first before channeling Death Ward to turn a team fight in his favor.

* Despite Jakiro's fragileness, he can easily harass Shadow Fiend with Dual Breath and Liquid Fire than Shadow Fiend can harass Jakiro with Shadowraze.
* Jakiro can easily cancel Requiem of Souls with Ice Path as Shadow Fiend is a very easy target while channeling it.
* Aghanim's Scepter upgraded Macropyre can deal pure damage-over-time and pierce spell immunity, which can discourage Shadow Fiend from even trying to initiate with Requiem of Souls.
Additional:
* Despite Jakiro's fragileness, he can easily harass Shadow Fiend with Dual Breath and Liquid Fire than Shadow Fiend can harass Jakiro with Shadowraze.
* Jakiro can easily cancel Requiem of Souls with Ice Path as Shadow Fiend is a very easy target while channeling it.
* Aghanim's Scepter upgraded Macropyre can deal pure damage-over-time and pierce spell immunity, which can discourage Shadow Fiend from even trying to initiate with Requiem of Souls.

* Death Ward can be easily canceled by Jakiro, or even turned against him with Macropyre, due to it's attack range being smaller then Jakiro's cast range. And Crystal Maiden, his Scepter does not allow him to move while using it. Voodoo Switcheroo is even easier to land Jakiro's Macropyro/Ice Path combo. And unlike Crystal Maiden, Witch Doctor's Aghanim's Scepter upgraded Death Ward does not allow him to move while using it.
* While Maledict can be quite effective on Jakiro, along with repetitive stuns from Paralyzing Cask, it is very difficult to get a strong Maledict on him. Although Witch Doctor's Paralizying Cask, Maledict and Death Ward combo will still quickly eliminate Jakiro.
* On the other hand. Voodoo Restoration will partly protect his allies from Jakiro spells, as it heals based on their Max Health once he gets his Talent (Level 25). Before then though, it won't make a dent in the damage Jakiro deals.

* Shadow Fiend's Requiem of Souls allows Rubick to output enormous crowd damage and control to the enemy team.
* Requiem of Souls has an effective range of 1000. Rubick can steal the spell out of the fear range with any level of Arcane Supremacy learned.
* Requiem of Souls has a significant cast animation which allows Rubick to predict the steal timing, since Shadow Fiend usually positions at the center of battlefield.
* Telekinesis can lift a unit right on top of Rubick with no collision size, forcing the victim to absorb all damaging lines of Requiem of Souls from Rubick, possibly resulting in a one-shot kill.
* Note that Requiem of Souls from Rubick still uses the original 1.67 second channeling time.
* It is advised to build Blink Dagger to jump in and cast Requiem of Souls given the opportunity.
* The three Shadowraze (Far) abilities are decent for farming and extra damage output.
* Note that Shadowraze (Near), Shadowraze (Medium) and Shadowraze (Far) are considered three separated abilities, only one is stolen per spell steal cast.
* It could be troublesome to cast Shadowraze (Far) immediately for damage output immediately after stolen since it is hard to react and recognize which of the three is stolen.
* Shadow Fiend's right click damage together with his ability damage may hurt Rubick bad. Consider items like Ghost Scepter and Glimmer Cape, together with wards to avoid being picked up.

* Witch Doctor's iconic Death Ward is a perfect spell for Rubick to output high damage.
* Death Ward requires channeling which makes Witch Doctor a clear tagret for stealing. Rubick can steal the spell outside of Death Ward's attack range most of the times.
* Note that an skilled Witch Doctor player can cast Voodoo Restoration to disrupt their last spell for Rubick to steal.
* Telekinesis can interrupt a channeling Death Ward. With Death Ward's high burst damage, combining Death Ward and Telekinesis to hold enemy in place can result in a solo kill in the early game.
* Paralyzing Cask provides an additional disable. The ability also helps moderately with farming.
* Voodoo Restoration provides some utility by healing Rubick and his team.
* Maledict is a damage-over-time nuke that amplifies the damage enemy taken.
* Telekinesis can reposition the enemy within the range of Maledict.
Additional:
* Rubick can steal Death Ward easily as it is a channeled ability and then use it to turn teamfight to his advantage.
* However, a skilled Witch Doctor will toggle Voodoo Restoration immediately after placing his Death Ward to prevent that.

* Bounty Hunter can absolutely destroy a Shadow Fiend's game by ganking his midlane with Shadow Walk, Jinada and Shuriken Toss.
* If his lane goes bad, a Shadow Fiend usually goes to the jungle. Follow him with Shadow Walk and take half of his experience.
* Due to its ministun, Shuriken Toss is a good way to interrupt Shadow Fiend's long cast animation on Requiem of Souls.
Additional:
* Shuriken Toss can be used to cancel Requiem of Souls.
* Shadow Walk and Jinada allow Bounty Hunter to gank Shadow Fiend early on
* Track prevents Shadow Fiend from escaping with Shadow Blade.

* Low mobility heroes: Heroes with no/little means of traveling fast have difficulty getting to/away from Bounty Hunter due to his slowing Jinada and hastening Track. Few examples of such heroes are: Crystal Maiden, Sniper, Ursa, Witch Doctor, etc.

* Enfeeble can be used to decrease Shadow Fiend's already abysmal level one damage even further, preventing him from getting farm and Necromastery stacks.
* Brain Sap allows Bane to heavily harass Shadow Fiend, even through debuff immunity from Black King Bar.
* Nightmare allows Bane to set up some early ganks onto Shadow Fiend.
* Fiend's Grip enables Bane to completely take Shadow Fiend out of a fight and potentially even kill him, even through Black King Bar.
Additional:
* Enfeeble can be used to decrease Shadow Fiend's already abysmal level one damage even further, preventing him from getting farm and Necromastery stacks.
* Brain Sap allows Bane to heavily harass Shadow Fiend.
* Nightmare allows Bane to set up some early ganks onto Shadow Fiend.
* Fiend's Grip enables Bane to completely take Shadow Fiend out of a fight and potentially even kill him, even through Black King Bar.

* Heroes that depend on disrupting fights with ability combos or big ultimate abilities are vulnerable to the long stun of Fiend's Grip: Disruptor, Death Prophet, Enigma, Faceless Void, Invoker, Lich, Magnus, Mars, Medusa, Outworld Destroyer, Phoenix, Puck, Queen of Pain, Shadow Fiend, Treant Protector, Underlord, Winter Wyvern, Witch Doctor, Zeus.

* Lina can outlanes Shadow Fiend on the central line, due to the fact that Lina's attack range exceeds the attack range of Shadow Fiend, which makes it difficult for him to fend off her attacks and approach creeps, thus Lina has more level and gold.
* Lina can defeat Shadow Fiend with the combination of her abilities on lane and during teamfights: Light Strike Array, Dragon Slave, Laguna Blade, Shadow Fiend does not have a large pool of health before buying items for extra strength and health like Satanic, which is why Lina's strong magic damage is enough to kill him quickly.
Additional:
* Outlanes Shadow Fiend on the central line, due to the fact that Lina's attack range exceeds the range of Shadow Fiend, which makes it difficult for him to fend off her attacks and approach creeps, thus Lina has more level and gold
* Defeats Shadow Fiend` from Burst with a combination of skills: Light Strike Array, Dragon Slave, Laguna Blade, Shadow Fiend does not have a large pool of health before buying an item: Satanic , which is why Lina's strong magic damage is enough to kill him quickly

* Heroes who have channeled abilities can be stunned by Light Strike Array, like Witch Doctor with Death Ward and Bane's Fiend's Grip.

Additional:
* Light Strike Array cancels out Death Ward from a long distance.

* Heroes that can gank Shadow Fiend in the early game: Earth Spirit, Nyx Assassin, Riki, Spirit Breaker.

* Without Dust of Appearance or Sentry Wards, Riki is able to silence Witch Doctor with Smoke Screen, and is likely to build a Diffusal Blade, leaving Witch Doctor without mana to cast Voodoo Restoration, as well as Skull Basher to interrupt Death Ward.

* Lucent Beam and Eclipse with ministun talent can be used to cancel Requiem of Souls if Shadow Fiend does not have Black King Bar. Likewise, since Shadow Fiend is prone to buying Blink Dagger, an ill-timed Blink Dagger can give Luna a free chance to counter-initiate with Eclipse.
* Moon Glaives and Lunar Blessing allow Luna to outfarm Shadow Fiend in lane and the high physical damage output they provide her can also help her deal with Shadow Fiend even when he buys Black King Bar in late game.
* A well timed Eclipse will burst and kill Shadow Fiend before he even either initiates or gets a chance to retaliate, especially when equipped with Aghanim's Scepter and Ethereal Blade, this could become even worse for Shadow Fiend if he does not have Black King Bar. But bear in mind however, that smart and skilled Shadow Fiend can buy Wind Waker to counter this issue.
* Even though Shadow Fiend can evade all of Luna's abilities with Shadow Blade, smart Luna will always buy Dust of Appearance to provide vision on Shadow Fiend to her and her team.
Additional:
* Lucent Beam and Eclipse with ministun talent can be used to cancel Requiem of Souls if Shadow Fiend does not have Black King Bar. Likewise, since Shadow Fiend is prone to buying Blink Dagger, an ill-timed Blink Dagger can give Luna a free chance to counter-initiate with Eclipse.
* Moon Glaives and Lunar Blessing allow Luna to outfarm Shadow Fiend in lane and the high physical damage output they provide her can also help her deal with Shadow Fiend even when he buys Black King Bar in late game.
* A well timed Eclipse will burst and kill Shadow Fiend before he even either initiates or gets a chance to retaliate, especially when equipped with Aghanim's Scepter and Ethereal Blade, this could become even worse for Shadow Fiend if he does not have Black King Bar. But bear in mind however, that smart and skilled Shadow Fiend can buy Wind Waker to counter this issue.
* Even though Shadow Fiend can evade all of Luna's abilities with Shadow Blade, a smart Luna will always buy Dust of Appearance to provide vision on Shadow Fiend to her and her team.

* Luna can easily cancel channeling spells with Lucent Beam and 0.25s Eclipse Lucent Ministun talent for Eclipse, she can also buy Abyssal Blade in case they decide to buy Black King Bar: Enigma's Black Hole, Witch Doctor's Death Ward, Shadow Shaman's Shackles, Lion's Mana Drain, Bane's Fiend's Grip, Pudge's Dismember, Crystal Maiden's Freezing Field, Pugna's Life Drain, Dawnbreaker's Solar Guardian, and Naga Siren's Reel In from Aghanim's Scepter.

Additional:
* Lucent Beam interrupts Death Ward from a decent range.
* With Dust of Appearance, Eclipse kills Witch Doctor during Death Ward, even through Glimmer Cape.

* Shrapnel can be used to cancel Shadow Fiend's Blink Dagger from a huge range.
* Take Aim and Headshot allow Sniper to harass Shadow Fiend in lane without getting into the range of his Shadowrazes.
Additional:
* Shrapnel can be used to cancel Shadow Fiend's Blink Dagger from a huge range.
* Take Aim and Headshot allow Sniper to harass Shadow Fiend in lane without getting into the range of his Shadowraze.
* Assassinate when upgraded with Aghanim's Scepter can be used to cancel Shadow Fiend's Requiem of Souls.

* Heroes with channeled abilities which Assassinate may cancel at long range: Witch Doctor, Crystal Maiden, Shadow Shaman, Pugna

* Doom has several disable abilities to choose from jungle creeps (e.g. War Stomp, Ensnare) to deal with Shadow Fiend who lacks escape abilities.
* When Doom combines creep abilities with Scorched Earth, Infernal Blade, and Doom, Shadow Fiend most likely will die as he cannot use Shadowraze and Requiem of Souls to protect himself, and also cannot even flee by using Shadow Blade or Blink Dagger.
* Although Shadow Fiend has a high physical damage output, Doom has a large health pool to survive it, meaning Doom's combo with high magical damage output will shutdown Shadow Fiend first.
* Doom usually buys Radiance to improve his damage, making his nuke combo more deadly to Shadow Fiend. The blind also prevents Shadow Fiend from landing his attacks often.

* 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.

* Dragon Tail can be used to cancel Requiem of Souls.
* Breathe Fire reduces Shadow Fiend's damage even further.
* Dragon Knight's high strength and Dragon Blood means that he'll be able to tank Shadow Fiend's right clicks.

* Death Ward does little damage against Dragon Knight's armor, and Dragon Knight's high health regeneration minimizes damage from Maledict.

* The Reflection of Shadow Fiend cause Presence of the Dark Lord to affect Shadow Fiend, reducing his armor and making it easier for Terrorblade to kill him. Shadow Fiend also doesn't have lots of survivability or control abilities in order to escape.
* If Shadow Fiend chooses to go for a physical damage item build, he'll have a hard time against Terrorblade's high armor.

* Witch Doctor's Maledict burst damage can be prevented by Sunder if timed correctly. But it can kill Terrorblade if he has no target to be Sundered with, especially in the early game.
* Death Ward deals physical damage, and Terrorblade's high armor can help him survive against Death Ward. However, Terrorblade has no disable in his skillset at all, and he cannot stop Witch Doctor from channeling Death Ward to maximum. And if Witch Doctor owns Aghanim's Scepter, attacks from Death Ward will be able to bounce around and wipe out Terrorblade's illusions and his team.
* Terrorblade must be careful as Paralyzing Cask is commonly tricky to dodge for him due to his reliance on illusions.

* 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.

* 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.

* Heroes who depend on attacks (such as Shadow Fiend or Drow Ranger) can be nullified by Fire Spirits' attack speed slow.

* Heroes with slow movement speeds and small health pools (supports like Crystal Maiden or Witch Doctor) are easy targets for Phoenix. Should they be inflicted by its DOT debuffs, they will be very quickly killed without even getting a chance to fight back.

* 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.

* Heroes that have a channeled ability that can be interrupted by Meat Hook: Shadow Shaman, Witch Doctor, Enigma, Bane.

Additional:
* Meat Hook interrupts Death Ward from a decent range, even through Black King Bar & Glimmer Cape.
* Pudge can survive the damage from Maledict because of his Flesh Heap stacks.
* However the damage-over-time from Rot is counteracted by Voodoo Restoration.

* 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.

* 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.

* Heroes that are hard to kill without lockdown: Puck, Weaver.

* Low health spellcasters: Lina, Witch Doctor, Tinker, Keeper of the Light, all rely heavily on their spells and are fragile heroes. They all also have avoidable spells, allowing Puck to get to them and quickly burst them down.

* The blind from Laser prevents Shadow Fiend from attacking for its duration, potentially preventing him from getting a kill.
* Scythe of Vyse can be used to prevent Shadow Fiend from casting Requiem of Souls.
* A combination of Tinker's abilities and his items (like the Dagon 5 and Ethereal Blade combo) can kill Shadow Fiend quickly.
Additional:
* During the laning stage Laser will reduce Shadow Fiend's last hits, preventing him from getting Necromastery souls.
* Shadow Fiend has low health and is vulnerable to Tinker's high magic burst.

* Guardian Angel protects allies from Death Ward's physical damage.
* Purification and Heavenly Grace will most likely save teammates from dying to Maledict.

* It is especially easy for Oracle to negate the damage from Maledict, and even heal through it with Fate's Edict and Purifying Flames.
* If by some miracle an enemy is still about to die because of Maledict, he can still save him with False Promise.

* Earthshock prevents Shadow Fiend from escaping after Ursa used his Blink Dagger to get on top of him.
* Overpower and Fury Swipes allow Ursa to quickly kill Shadow Fiend.
* Enrage keeps Ursa alive in a manfight with Shadow Fiend and allows him to stay close, even if Shadow Fiend uses Requiem of Souls.

* Berserker's Call and Counter Helix allow Axe to kill Shadow Fiend if he stands too close to a creep wave.
* Battle Hunger is can be strong against Shadow Fiend in the early game because Shadow Fiend's low attack damage makes it hard for him to get last hits if he has no mana. However, Shadowraze also makes it very easy for him to get last hits, so use with caution.
* Axe's naturally high strength and health regeneration will be enough to tank a lot of Shadow Fiend's damage in the early game.

* Void can be used to cancel Requiem of Souls.
* Crippling Fear prevents Shadow Fiend from using Shadowraze or Requiem of Souls.
* With Dark Ascension and Gem of True Sight, Night Stalker can find and kill Shadow Fiend easily. He is also a tanky hero that can fight Shadow Fiend at any stage of the game.

* Wraithfire Blast cancels Death Ward in decent range.
* Death Ward is meaningless while Reincarnation is off cooldown.
* Vampiric Aura can out-heal the {tooltip:DoT|Damage over Time} from Maledict.

* Vengeful Spirit has two abilities to interrupt Death Ward, even through Black King Bar.

* Glimpse and Kinetic Field allows Disruptor to set up some early kills onto Shadow Fiend.
* Static Storm can be used to cancel the cast of Requiem of Souls.

* Charge of Darkness allows Spirit Breaker to gank Shadow Fiend in the early game, preventing him from getting Necromastery stacks.
* Nether Strike and Charge of Darkness can be used to prevent Shadow Fiend from casting Requiem of Souls.

* Static Link can steal Shadow Fiend's high physical damage output from Necromastery, lowering his damage output, and Static Link cannot be prevented by Black King Bar.
* Plasma Field and Eye of the Storm can melt down Shadow Fiend easily, due to his low health.

* Decrepify prevents Shadow Fiend from attacking for its duration, potentially preventing him from getting a kill.
* Nether Ward can do heavy damage to Shadow Fiend if he tries to cast his Requiem of Souls and his Shadowraze.
Additional:
* Decrepify prevents Shadow Fiend from attacking for its duration, potentially preventing him from getting a kill.
* Nether Ward can do heavy damage to Shadow Fiend if he tries to cast his Requiem of Souls or spam Shadowraze.

* Beware of placing the Death Ward if Chronosphere is off cooldown, as it will cancel the effect and leave Witch Doctor vulnerable if he does not react in time.

* 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.

* Arc Lightning allows Zeus to get farm in lane against Shadow Fiend without coming into the range of his Shadowrazes.
* Lightning Bolt can be used to heavily harass Shadow Fiend when he tries to get a last hit.
* Thundergod's Wrath and Lightning Bolt can be used to detect Shadow Fiend if he tries to escape with Shadow Blade.

* Shadow Fiend's fragility and lack of a natural escape mechanism makes him a great target for Templar Assassin's Meld.
* Shadow Fiend's burst damage, such as Shadowraze and Requiem of Souls, is easily nullified by her Refraction.

* 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

* Sacred Arrow can be used to interrupt Death Ward from a safe distance, forcing him to cancel it to dodge or get hit.
* Paralyzing Cask is a slow-moving stun, and Mirana can Leap away from her allies to keep it from bouncing.
* Witch Doctor has low health and can easily be killed with an Aghanim's Scepter combo or just when hit with an arrow.

* Shadow Fiend's lack of mobility and low base health make him an easy target for early ganks.

* Requiem of Souls is easily interrupted by Boundless Strike, due to its long cast time.
* Shadow Fiend's lack of mobility and escape makes him an easy target to ambush with Primal Spring, especially during laning stage.
* Being close means he cannot use all three razes on you before you get your Jingu Mastery stacks.

* Paralyzing Cask's short stun rarely prevents Monkey King from ambushing Witch Doctor.
* Death Ward's long channel is easily interrupted by Boundless Strike.

* Morphling can Attribute Shift to strength after being hit by Maledict. Since Maledict deals its damage based on the difference between HP on cast and HP after two seconds, odds are Morphling will have more HP than when Maledict was cast, thus resulting in no damage.
* On the upside, players prone to panicked reactions may Morph to agility, making Maledict even more efficient than intended.
* Adaptive Strike (Strength) can interrupt Death Ward at a decent range.

* Arc Warden's Magnetic Field dodges all damage from Death Ward.

* Stone Form can easily interrupt heroes with long channeling spells, like Crystal Maiden, Bane, Witch Doctor, or Enigma.

* 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.

* Late game heroes are Sven's favourite kind of opponent, such as Anti-Mage, Spectre and Shadow Fiend.

* Generally, any fragile heroes will have a hard time dealing with Undying's tankiness, and even more so if Decay is used on them. Some examples are Crystal Maiden and Witch Doctor.

* 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.

* Heroes with channeled abilities can be interrupted by a long-range Fissure: Crystal Maiden, Witch Doctor, Bane, Pugna, Pudge.

* Heroes with long channeling abilities like Witch Doctor are easy targets for Kunkka to interrupt in team fights.

Additional:
* Torrent can cancel Death Ward from a far distance.

* Heroes that can gank Shadow Fiend in the early game: Earth Spirit, Nyx Assassin, Riki, Spirit Breaker.

* Fragile support heroes are all ideal targets for the Phantom Assassin. Heroes such as Lina and Witch Doctor are all prime targets that may not be able to react quickly and fight back due to Phantom Assassin's sudden appearance.

* Death Ward's first target (before it bounces) can evade it, therefore Windranger and Phantom Assassin are poor choices to use it on.

* Heroes that are hard to kill without lockdown: Puck, Weaver.

* Heroes like Slark, Witch Doctor and others also tend to suffer in Ice Blast's heal denial.

* 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.

* Heroes with high burst damage: Lina, Lion, Luna, Nyx Assassin, Queen of Pain.

* Heroes who cannot escape from Trample early might be easy first blood. Heroes like Witch Doctor and Omniknight should play very cautiously alone...

* Squishy heroes or heroes without hard disables or silences: Shadow Demon, Shadow Fiend, Venomancer, Ancient Apparition etc.

* Heroes with high burst damage: Lina, Lion, Luna, Nyx Assassin, Queen of Pain.

* Squishy core heroes (Shadow Fiend, Sniper, etc)

* Heroes with long animations can be frequently interrupted with Cold Snap: Earthshaker, Monkey King, Shadow Fiend Lina

* Heroes with powerful channeling abilities are easily interrupted by Phantom's Embrace: Bane, Pudge, Witch Doctor, Crystal Maiden, Enigma.

* Heroes who rely on channeling abilities can be interrupted in teamfights by Rolling Thunder: Crystal Maiden, Pugna, Witch Doctor

* Heroes with plenty of summons, such as Broodmother or Nature's Prophet can have their minions soak up most of your Paralyzing Cask.

* 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.

* Heroes with plenty of summons, such as Broodmother or Nature's Prophet can have their minions soak up most of your Paralyzing Cask.

* 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.

* Heroes who build mana boosting items but have low mana regeneration are especially vulnerable against Mana Break and Mana Void: Timbersaw, Slark, Shadow Fiend, Clinkz, Bristleback Nyx Assassin, Magnus

* Like any hero with a channeled spell, Last Word is a counter to it.
* Global Silence goes through spell immunity and prevents Witch Doctor from casting his spells.

* Large area-of-effect with delay or require channeling: Enigma, Crystal Maiden, Invoker, Shadow Fiend, Pugna, Keeper of the Light, Dawnbreaker.

* 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.