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