Here is the full list of all 57 FIST OF AWESOME achievements.
Watch to the end of the credits
Play 50 games in Arena Mode
Play 25 games in Arena Mode
Stay alive for 3 minutes in Arena Mode
Stay alive for 4 minutes in Arena Mode
Stay alive for 5 minutes in Arena Mode
Stay alive for 2 minutes in Arena Mode
Stay alive for 1 minute in Arena Mode
Complete story mode on Easy difficulty
Select the lumberdude as Tim's fiancee
Complete the last stage
Die and restart 10 times in story mode
Complete Forbidden Zone
Reach the fake ending
Complete Time Train
Complete Hammertime Station
Complete Castle
Complete The King's Road
Complete Musty Cave
Complete Volcanic Plains
Complete Human Zoo
Take out 100 belligerent bears
Complete Bearhattan
Complete Tutorial / Woodland
Slay your first enemy
Pause and resume the game
Take out 1000 belligerent bears
Take out 5000 belligerent bears
Take out 10000 belligerent bears
Complete story mode on Hard difficulty
Complete story mode on Harder difficulty
Complete game without using a continue
Max out Tim Burr's abilities
Max out Clive's abilities
Max out Lumberbear's abilities
Max out Rembrandt's abilities
Max out Cochise's abilities
Max out Will's abilities
Max out Tommy's abilities
Max out Scratchy's abilities
Max out Trevor's abilities
Max out Cave Bear's abilities
Max out Frederick's abilities
Max out Rodrigo's abilities
Max out King Bear's abilities
Max out Bartholomew's abilities
Max out Jimbo's abilities
Max out Candy's abilities
Max out Desire's abilities
Max out Brian's abilities
Max out Brian Bear's abilities
Max out Santa's abilities
Reach maximum level for all characters
Play 100 games in Arena Mode
Play 250 games in Arena Mode
Play 500 games in Arena Mode
Select the lumbergirl as Tim's fiancee