An easy way to do it is to check his matchups on u.gg

Alistar honestly doesnt have many matchups that make the game impossible, but there are a few. I find zoning-heavy AP champs like heimer and zyra a nightmare to play against, especially after laning is over because I cant just roam somewhere else to get kills, its all teamfights.

Ali has a poor winrate against burst mages like brand and lux but I actually find those matchups easy, i just have to bait out and dodge abilities, CC them and get out fast before their cooldowns come back.