Here is the full list of all 49 Muck achievements.
Kill 100,000 mobs
Kill 250 buff mobs
Kill 10,000 mobs
Swim 25km
Jump 10,000 times
Beat the game without any players picking up a powerup
Beat the game on gamer difficulty
Beat the game in less than 10 days on Gamer mode
Beat the game with 2 players, but no one can take any damage (Normal diff or harder)
Beat the game alone without taking any damage (Normal difficulty or harder)
Beat the game using only a rock, taking no damage and using no powerups. This goes for all players in lobby. (Normal or harder)
Beat the game using only a rock as your weapon / tool. This goes for all players.
Die 100 Times
Beat the game with 8 players, but no one can take any damage (Normal diff or harder)
Beat the game with 4 players, but no one can take any damage (Normal diff or harder)
Survive for 100 days
Start 200 battle totems
Wield the Night Blade
Beat the game in less than 8 days
Die 50 Times
Beat the game on normal difficulty
Collect all 5 gems
Beat the game on easy difficulty
Leave Muck
Slay 1000 goblins
Kill 200 enemies using bows
Kill 250 cows
Walk 250km
Kill 1,000 mobs
Find and wishlist Karlson in Muck
Defeat Gronk
Slay all bosses
Open 500 chests
Build 250 builds
Defeat big chunk
Die 25 times
Pick up 10 Milk powerups in one game
Craft 1,000 coins
Defeat Guardian
Defeat Chief
Drown
Open Chiefs chest
Eat 50 red shrooms without growing bigger
Kill 100 mobs
Die 10 times
Revive a teammate
Kill a friend on Survival Mode
Play Muck for the first time