Alchemist/Counters

Bad against...

 * cancels out 's rapid health regeneration. The same can screw over  toggling, as it will make HP drain insanely fast, essentially killing the bearer in no time.


 * greatly reduces 's attack speed advantage.


 * can kill Alchemist before has the time to heal him.


 * , followed by take advantage of Alchemist's low base armor, making it easy to quickly kill him with physical damage.


 * - Invoker can win the mid lane easily against Alchemist because regeneration will nullify 's damage over time and  damage bonus will allow Invoker to out last hit Alchemist.

Others

 * can bully out of mid lane quite easily, forcing him to either retreat into jungle, or stay harassed in lane, and get very few last hits.
 * can take advantage of 's little armor to kill him.
 * 's makes sure that either  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.

Items

 * reduces 20px's already low base armor even further, and protects against his rapid physical attacks.
 * reduces 20px's attack speed and gives a fair amount of armor.
 * is a troublesome item for many physical carries, as they are unable to hit anyone for some time, unless they can dispel it; is no exception.
 * disables, making sure he won't be able to use his to heal up, and allows heroes to burst him down fast.
 * Someone who is vigilant of can use  to reflect it back at.

Good against...

 * 's abilities rarely do enough damage to seriously harm Alchemist.


 * kills Phoenix very quickly in.


 * will take down in no time.
 * Alchemist can also farm the zombies for easy gold.


 * 's health regeneration and attack speed bonus will make fail.


 * will decrease Meepo armor, good combo with.
 * is good to stop Meepo because his lack of spell immune.
 * allows for quick kills before Meepo can away.


 * His low HP allows Alchemist to take out him fast.
 * and combo to farm treants easily.

Others

 * Any carry heroes because they disadvantage to get money and in fight.
 * Entry

Works well with...

 * combined with makes Alchemist attack at insane speeds.


 * and will purge debuffs away.
 * combined with may give you some serious sustainability.
 * is an aoe purge, which will remove from enemies buffs like and, and also root them.


 * Stone Gaze makes Alchemist can kill their enemies with Acid Spray and Chemical Rage.


 * A well timed Echo Stomp will allow Alchemist to set up his Unstable Concoction safely without worry of self-stunning while looking for a target.


 * Alchemist using his Chemical Rage for kill confused enemies whom handled Spectre's Haunt.


 * Both are tanker, so they can initiate both by Unstable Concoction and Ravage which cause double stun (or triple if Tidehunter has Refresher Orb). More reason is Alchemist can gives Tidehunter Scepter and Moon Shard which make him stronger and more powerful Gush and Ravage.

Others

 * Alchemist works well with any hero that has an upgrade, as he can farm it for them (most likely far more quickly) and also free up an inventory slot.
 * Omniknight's Repel cancel self stun from Unstable Concoction.
 * Entry

List of heroes that counter Alchemist, and list of heroes that work well with Alchemist.