Here is the full list of all 15 FallenCore achievements.
Successfully complete first level
Pull the lever while playing as zombie at level 7
Turn on the screen at level 14 and get the error message
Smash zombie and yourself by one piston
Die more than 100 times
Get killed by sealing after a jump from springer
Die while you controlling an enemy
Kill the zombie at the up in level 7 before you will be controlling him
Solve a puzzle with prism
Get yourself to level 21
Defeat The Engineer
Defeat The Freezebot
Kill an enemy by throwing him in a hole
Fall from a big high and do not die
Name yourself Ardi