Here is the full list of all 13 Chess Survivors Playtest achievements.
Kill 1000 non-elite enemies
Kill 1000 elite enemies
Win a game on Quick Speed
Win a game on Fast Speed
Win a game on Uber Speed
Win a game on Blitz Speed
Win a game playing as Joker
Win the game playing as Evil Monkey
Win a game playing as Creep Doll
Win a game playing as Smol Wizard
Win a game playing as Jak
Win a game playing as Fish in a Bowl
Win a game playing as Sneezy Ghost