Here is the full list of all 12 The Forgotten Ones achievements.
Something is burning...
You killed the tourists.
Beaten the game.
Schienzel is forever dead.
Got the FG-42.
You spared the tourists.
Got the meat cleaver.
Got the SVT-40.
Found the book of darkness.
You did what was necessary.
Use an healthkit at low health.
Discover the ritual room