* Both Guardian Angel and Purification are perfect counters against Duel.
Additional:
* Purification prevents Legion Commander from killing her target, and will always hit her during Duels.
* Guardian Angel completely wastes Duel's duration, and can save an ally across the map when upgraded with Aghanim's Scepter.

* Heroes who rely strongly on melee physical damage will fare badly against Omniknight's Guardian Angel: Sven, Phantom Assassin, Juggernaut, Dragon Knight, Lycan, Ursa, Troll Warlord

* Bane's Enfeeble makes Ursa more susceptible to disables as it reduces Status Resistance.
* Bane can use Nightmare and Fiend's Grip to lock down Ursa early game and in team fights, forcing Ursa to buy a Black King Bar and making him very vulnerable to being kited once his Black King Bar is down to 5 seconds.
* Overall, Bane's potent disables force Ursa to build more defensive items and play more defensively in general.

* Enfeeble, Nightmare and Fiend's Grip all prevent Legion Commander from winning Duels, especially when Bane has Blink Dagger.
Additional:
* Bane has powerful single-target abilities that can help his allies win Duels, or at least cripple Legion Commander for the duration.
* Nightmare can waste Duel's entire duration as the dueled units transfer the Nightmare back and forth. This may be prevented if a non-Dueling unit attacks the Nightmared Dueler.

* Heroes who can hide the Dueled target (Outworld Devourer, Shadow Demon, Tusk, Phoenix with Aghanim's Scepter etc).

Additional:
* Outworld Devourer can save an ally hero caught by Duel with Astral Imprisonment, and he can inflict heavy damage on Legion Commander with Arcane Orb to aid his ally. However, if he gets caught, he is unlikely to survive the duel, due to his lack of durability.

* Ursa struggles against heroes with strong (and especially undispellable) disables (Disruptor, Puck, Shadow Demon, Outworld Devourer and etc).

* Wave of Terror can reduce Legion Commander's survivability during a Duel.
* Magic Missile and Nether Swap disrupts Duels and saves allies.

* 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.

* Gravekeeper's Cloak protects Visage from Legion Commander's attacks for most of Duel's duration.
* Chain stuns from Visage's familiars prevents Legion Commander from winning Duels.

* Primal Roar and the slow from Boars makes kiting Ursa very easy.

* God's Strength with Sven's tankiness and item build makes him difficult to take down in Duels.
* Storm Hammer can be used to interrupt Duels (until Legion Commander buys Aghanim's Scepter).
* Sven also has a talent at level 15 that allows Storm Hammer to apply a basic dispel on any enemies hit by it, which can remove the buffs from Overwhelming Odds and Press the Attack.
* Warcry gives a shield to Sven's teammates, which can completely waste Duel's duration depending on how much strength Sven has.

* Storm Spirit can steal Aegis of the Immortal during Roshan attempts through the Pit, because of his Ball Lightning.
* Ursa has no way to catch a slippery Storm Spirit, as Earthshock's slow will do nothing to stop Storm Spirit from using Ball Lightning.

* Decrepify on either hero stops Legion Commander from completing a Duel, and dissuades her from initiating Duels on ethereal allies.
* Life Drain can help Pugna's teammates win a fight, either by killing Legion Commander or replenishing her target's health.
Additional:
* Decrepify prevents Legion Commander from attacking allies during Duel, regardless if it's used on her or on the ally .
* Pugna can easily cast Decrepify, Nether Blast and Life Drain on Legion during the 4/4.75/5.5/8 seconds of duel

* Mystic Flare can easily burst down Legion Commander while she is Dueling.

* Windranger can avoid Ursa's primary source of damage, Fury Swipes, by simply using Windrun. The slow from Earthshock is also rendered irrelevant by Windrun.
* Focus Fire and Windrun can be used to kite Ursa.
Additional:
* Ursa relies on the Blink-Earthshock combo to slow enemies to burst them, but Windranger can use Windrun to escape through Earthshock's duration.
* Windrun and Focus Fire can easily allow Windranger to kite Ursa and do good amounts of damage in the process.

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

* Static Link drains Legion Commander's accumulated damage, effectively neutralizing her overall primary advantage, and prevents her from winning Duels.
* Storm Surge's movement speed buff makes Razor and his allies harder to catch and initiate on.
* Eye of the Storm, if used beforehand, will always hit Legion Commander during Duels, due to her forced proximity. This drastically lowers her survivability during Duel.

* Earthshaker's AoE stuns can save ally against Duel, forcing Legion Commander to spend Aghanim's Scepter or Black King Bar.

* Cold Embrace saves allies from dying in Duels.
* Winter's Curse turns Legion Commander's high damage against her allies, giving the enemy team little time to react.
* However, Winter Wyvern lanes very poorly against Legion Commander due to Press the Attack removing all the debuffs she can give. Winter Wyvern also has little chances of surviving if she gets Dueled herself.
Additional:
* Cold Embrace is very effective against Duel.
* Also, casting Winter's Curse at Legion Commander while an ally is in a Duel will stun her for most of the duration, possibly preventing lethal damage dealt to your ally. It can also turn her high-damage against her teammate.

* Aphotic Shield and Mist Coil makes it hard for Legion Commander to kill Abaddon's teammates in Duels.
* Borrowed Time makes Abaddon nearly impossible to kill in Duels, and often replenishes much of his health because Legion Commander cannot manually stop attacking during Duels.

* Doom makes Ursa less disruptive, and it cannot be dispelled with Enrage upgraded with Aghanim's Scepter.
* Aghanim's Scepter upgraded Infernal Blade can break Fury Swipes, negating much of his damage output.

* If Ursa uses Enrage Brewmaster can use Cyclone to render him harmless during his ultimate.
* Brewmaster has two spells to slow down Ursa, allowing his team to kite around him easily.

* Lucky Shot can disarm Legion Commander and reduce her armor, which can reduce her chances of winning a duel. If an ally is targeted, Pangolier can simply use Swashbuckle to inflict it on her.
* If an enemy Pangolier casts a well-timed Rolling Thunder before Legion Commander can cast Duel, it might result in her chasing down Pangolier until his or her ultimate ends, whichever duration ends first, resulting in an open window for enemy allies to target Legion Commander, making her vulnerable and susceptible to any source of attacks. If Legion Commander has an Aghanim's Scepter in her inventory, the risk of wasting a solid 8 seconds would result in a futile duel.

* Lion has two low cast point disables (Hex and Earth Spike) to control Ursa before he buys a Black King Bar.
* Hex is one of the few abilities that cannot be dispelled even with an Aghanim's Scepter upgraded Enrage.
* Lion can control Ursa's low mana pool via Mana Drain.

* Heroes with long or multiple disables will prevent Legion Commander from winning Duels: Shadow Shaman, Lion

* Walrus PUNCH! makes Legion Commander lose Duel easily, especially when she doesn't have Blade Mail. Tusk can also snowball dueled allies, preventing them from taking damage for a large portion of the duel's duration.

* Shallow Grave prevents Legion Commander from killing her opponents in Duels.
* Shadow Wave will heal an ally caught in a Duel, as well as dealing damage to Legion Commander.

* When Legion Commander uses Duel on one Meepo, he can use his other Meepos to kill her. If he wasn't dueled, he can help the teammate who was duelled to give the teammate the damage instead of Legion Commander.
* However, if Legion Commander picked up an Aghanim's Scepter and she duels one Meepo, that might be the end of Meepo if Legion managed to gather enough damage from previous duels.

* Slark can detect early Roshan attempts due to Shadow Dance if he frequently checks the Pit.
* Enrage cannot restore attributes stolen by Essence Shift and will reduce his physical damage output.
* Even if Ursa initiates with Earthshock, Slark can Pounce away or use Dark Pact after Ursa's initiation to avoid Fury Swipes' damage until Earthshock's slow is gone.

* Enchant dispels Overpower.
* Enchant's slow can help kite Ursa in fights and also in lane.
* Enchantress can out harass Ursa in lane by using her long attack range and Untouchable, as well as out sustaining him with Nature's Attendants.

* Riki can detect early Roshan attempts because of Cloak and Dagger if he frequently checks the Pit.
* Ursa cannot Enrage when in Smoke Screen (Black King Bar will help though).
* Even if Ursa gets vision over him, Riki can Blink Strike away or use Tricks of the Trade after Ursa's initiation to avoid all Fury Swipes damage until Earthshock's slow is gone.
Additional:
* Riki can detect early Roshan attempts because of Cloak and Dagger if he frequently checks the Pit.
* Ursa cannot Enrage when caught in Smoke Screen and will miss his attacks (although Black King Bar will help with this issue).
* Even if Ursa gets vision over him and initiates with Earthshock, Riki can Blink Strike away or use Tricks of the Trade after Ursa's initiation to avoid Fury Swipes' damage until Earthshock's slow is gone.

* Heroes with abilities that blind or cause Legion Commander to miss will prevent her from winning Duels: Arc Warden, Keeper of the Light, Riki

* Heroes who can provide constant vision inside the Roshan Pit can negate one of the strongest advantages of Ursa, which is the possibility of quickly killing Roshan at the early game, with minimum itemization needed (Clockwerk, Beastmaster, etc).

* Battery Assault's mini-stuns can severely disrupt Legion Commander's attack animation when she enters a Duel, potentially saving Clockwerk (or his allies) and possibly even giving him an edge in securing a win himself.
* Power Cogs pushes Legion Commander away from Clockwerk's allies when she enters a Duel.

* Wraith King's Reincarnation allows him to severely punish Legion Commander after he revives, as her abilities are on cooldown. Legion Commander is still awarded a Duel win if Wraith King reincarnates.

Additional:
* Wraith King makes a poor Duel target, as he can be already quite hard to bring down once, and then you have to worry about his second life.

* Clinkz, Sniper, Lone Druid, Troll Warlord, Legion Commander, Wraith King and others are some of the Heroes that bases themselves on attacks with little or no spell power, suffering in the grassy hands of Overgrowth.

Additional:
* Living Armor's global range makes it nearly impossible for Legion Commander to win Duels in the early to mid-game.

* Heroes that rely on slows to get kills: Lifestealer, Night Stalker, Ursa,...

* Heroes with global abilities can give Legion Commander's opponent an edge in Duels from anywhere on the map: Nature's Prophet, Ancient Apparition, Zeus, Invoker, Treant Protector

* Troll Warlord's melee bash and high attack speed can often help him and his allies win Duels against Legion Commander.

* Heroes who can delivers a big chunk of damage in few hits will find themselves struggle against Templar Assassin's Refraction: Sven, Phantom Assassin, Ursa, Wraith King, Lifestealer

Additional:
* Templar Assassin usually places Psionic Traps inside the Roshan Pit (and can teleport herself to the traps with an Aghanim's Scepter), preventing Ursa from killing Roshan without getting noticed by the enemy team.

* Ursa struggles against heroes with strong (and especially undispellable) disables (Disruptor, Puck, Shadow Demon, Outworld Devourer and etc).

* Assuming they have not bought anti-evasion items, attack dependent heroes such as Viper, Ursa or Clinkz can be a minor threat for Phantom Assassin early in the game, and may even be completely dominated by her thanks to her evasion.

* 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.

* Heroes that lack burst damage will have a difficult time taking down Monkey King, and fare badly against Jingu Mastery: Legion Commander, Lifestealer, Weaver, Wraith King

* Ursa struggles against heroes with strong (and especially undispellable) disables (Disruptor, Puck, Shadow Demon, Outworld Devourer and etc).

* Heroes who can hide the Dueled target (Outworld Devourer, 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.

* Heroes who rely heavily on melee attacks and lack early spell immunity are easily blocked and interrupted by Ink Swell: Lycan, Ursa, Troll Warlord.

* Heroes with global abilities can give Legion Commander's opponent an edge in Duels from anywhere on the map: Nature's Prophet, Ancient Apparition, Zeus, Invoker, Treant Protector

* Sprout is good for trapping melee carries with no escape abilities: Sven, Ursa, Alchemist, Lifestealer etc.

* Fate's Edict prevents Legion Commander from attacking for a few seconds, potentially saving Oracle's ally.
* Fortune's End dispels Press the Attack's healing and attack speed buff, as well as the movement speed bonus from Overwhelming Odds.
* False Promise protects allies and prevents Legion Commander from winning Duels and gaining bonus damage.
Additional:
* Provided that the enemy team does not have an Axe, Oracle can guarantee that his ally survives for the duration of the Duel with False Promise and has decent nuke potential to help ally to win a Duel. He can also disarm Legion Commander with Fate's Edict.
* Oracle can dispel enemy buffs like Overwhelming Odds and Press the Attack with Fortune's End.

* Lycan's ultimate makes him immune to slows from Ursa's Earthshock as well as allowing him to outmaneuver Ursa during Enrage. Lycan can also easily chase down Ursa while shapeshifted, should Ursa try to flee.

* Provided Luna is able to cast it in time, Eclipse can help win a Duel from Legion Commander.
* If Luna isn't the target, she can easily use Lucent Beam and Eclipse to win the fight for the ally.
Additional:
* A well-timed Eclipse before a Duel usually prevents Legion Commander from winning Duels, if Luna is the target.
* Meanwhile, when Luna is not a target, Eclipse and Lucent Beam can also help an ally win a Duel against Legion Commander.
* However, skilled Legion Commander players will always have a Black King Bar or Aghanim's Scepter handy since both abilities do not pierce through spell immunity.

* Song of the Siren lasts long enough to prevent a successful Duel (but only if Naga wasn't the target).