Here is the full list of all 21 GARAGE: Bad Trip achievements.
Complete the Arena Challenge
Complete the Skirmish Challenge
Complete the Axe-man Challenge
Complete the Labyrinth Challenge
Find all the parts of Demikhovsky's diary
Watch a TV show
Score a goal with your head
Beat the game
Kill Demikhovsky
Pick up soap in the shower room
Kill Dreadnought
Ride the train
Unlock a combination lock
Find a condom
Dispose of the old boss
Kill the centipede
Open the shelf in the desk
Find a secret passage
Take "heavenly" pills
Smash 15 vending machines
Kill your first cadaver