"Fix" for Broken Achievment
You need "Achievment Hunter: Begins".
Install it,after that copy the File:

"Steam\steamapps\common\Achievement Hunter Begins\Achievement Hunter_Begins_Data\Managed\Assembly-CSharp dll"

to:

"Steam\steamapps\common\Achievement Hunter Darkness\achievementhunter_darkness_Data\Managed"

Start the Game and the broken Achievment will drop