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