Phantom Assassin is one of the best carries to counter Anti-Mage. PA can kill AM with her burst physical damage, and chase with Phantom Strike if he tries to blink away.
When fighting against Anti-Mage, the best choice is shutting him down in the early game with a good offlaner and successful ganks, but that isn’t always possible.
If you are playing in solo queue as a carry, Phantom Assassin is an optimal hero to deal with AM throughout the match.
Let’s understand what makes PA such a great counter, the must-have items against AM, and your best teammates.
High burst physical damage
450% critical damage thanks to Coup de Grace
With Spell Shield, AM possesses a huge magic resistance - boosted even more by the level 25 talent.
Physical Damage is the best way to kill him, and PA glorious critical hits are an amazing tool. Often he won’t have the time to blink away.
Attack Speed bonus with Phantom Strike
You must kill Anti-Mage while he is under the effect of your team’s disables - otherwise, he will probably blink in a safe position and survive.
You don’t know if the team will have enough disablers, or if they know what to do, so speed is the key. 4 attacks with +130 bonus attack speed are often enough to proc 1 or more critical hits and a bash.
Phantom Strike to counter Blink
It is a rather effective skill to chase Anti-Mage if he survives to your ambush and blinks away. It is less effective at night because requires vision on the target, but the 1000 cast range is almost as much as Anti-Mage’s Blink - which is 1150 without the talent.
Armor reduction from the level 15 talent Armor Corruption
The new talent introduced in v7.07 reduces the enemy armor by 4 upon attack land, before the damage is applied. The lower the enemy armor, the higher your critical damage, thus you really want to melt his defense.
Monkey King Bar or Silver Edge to counter evasion
Almost all players buy a Butterfly on Anti-Mage because it is perfect for the hero: both AM and his illusions get damage, attack speed (via agility), and evasion.
You need one of the above mentioned items to disable it. Notably, the Silver Edge disables all the target passive abilities for 5 seconds, making him susceptible also to magic. Alert your casters about this opportunity - they will thank you.
The 7.07 Monkey King Bar is similarly efficient to the old one against heroes that get evasion only through the Butterfly (35%). You can find the complete analysis - against heroes and buildings - in my article. Do not neglect this item!
Desolator to boost your damage
As already explained, armor reduction greatly benefits your damage - you need this item against AM.
Abyssal Blade for a guaranteed stun
Disables are absolutely necessary to deal with AM, and the Abyssal Blade is your best option thanks to the 2 seconds stun. Of course, this is a late game item, but a cheap Skull Basher after the Desolator will already be of great help.
What you want from the Team
All heroes with reliable and long disables are immensely valuable in this hunt. Even if you disable AM passives with the Silver Edge, he will just run away without a good stun. All your damage has no use if you can't hit the target.
Armor reduction via skills
There are multiple heroes with skills that can reduce armor. A great example in 7.07 is Vengeful Spirit, a support that became more popular after all the talent buffs brought in by the Dueling Fates update. Her ability Wave of Terror decreases the armor of all enemies hit by 7 (8 with the level 10 talent).
Vengeful Spirit has an optimal skill-set to fight against Anti-Mage. Beside the armor reduction, she has a stun, an aura to increase the team’s physical damage, and a 1200 range swap ability to bring back AM if he blinks away.
Armor reduction items
The cheapest option is the Medallion of Courage - later on upgraded to Solar Crest. For 1175 gold the medallion diminishes the enemy armor by 7, and any support or ganker can easily include it in their item build.
A more expensive, but also great item for the team, is the Assault Cuirass. It gives 5 armor reduction through the Assault Aura in a 900 range AoE, plus attack speed and armor for the team - which will help PA even more.