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