Here is the full list of all 15 The Donnerwald Experiment achievements.
Nein!
Die inside a dream
Lie to your brother when it really matters.
Get spoiled about the ending (not really).
Use Montgomery's requiem skill while there are 3 or more valid targets and all ghosts randomly aim for the same target.
Trust in the high chance of survival.
Make Erika and Johanna declare a Diplomatic Insult war upon each other.
-1 stability
Lose Max HP.
Pet the fox.
Win a love battle.
Fire the railgun with 20 or more buff power.