Here is the full list of all 19 Gang Beasts achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
Climb to the highest section of the buoy on the buoy stage
Break the cables supporting an elevator without falling on the elevators stage
Escape from the incinerator hazard on the incinerator stage
Get inside a truck on the trucks stage
Climb onto the roof of a truck on the trucks stage
Defeat an enemy wave in the waves game mode
Escape from a grinder hazard on the grind stage
Customise a character on the character customisation screen
Get inside a shipping container on the containers stage
Escape from the water on the buoy stage
Concuss an enemy with a diving headbutt
Concuss an enemy with a diving kick
Win a game of football without the opposition scoring in the football game mode
Break the cables supporting a container without falling on the containers stage
Break the cables supporting a gondola without falling on the gondola stage
Pass through the orange chute on the girders stage
Collide with the seating and the railings on the ring stage
Pass through three road signs on the trucks stage
Break the stairs on the towers stage