Here is the full list of all 20 The Lost Cube achievements.
Died for the first time
Died 20 times
Died 50 times
Died 100 times
Collected your first guitar pick
Collected 5 guitar picks
Collected 15 guitar picks
Collected 30 guitar picks
Killed by a laser beam
Killed by an angry viking
Killed by a green slime
Killed by a bat
Killed by a frog
Fell in a pit of acid
Killed by a cricket
Killed by a flying creeper
Killed by a crawler
Completed the first chapter
Completed the second chapter
Completed the third chapter