Here is the full list of all 21 Action Henk achievements.
Fall into the lava.
Defeat Kentony's challenge.
Defeat Betsy's Challenge.
Publish a level to the Steam Workshop.
Beat Neil's Challenge.
Beat Cedar's Challenge.
Beat Kentinator's Challenge.
Beat Action Henk in the City.
Earn a Bronze medal on all levels.
Earn a Silver medal on all levels.
Earn a Gold medal on all levels.
Earn a Rainbow medal on all levels.
Beat all bonus levels
Challenge a friend to beat your score.
Ragequit the game during a level.
Beat 99% of all players on a level.
Jump over the barrier.
Win a multiplayer match.
Press reset over 9000 times.
Die 100 times.