Here is the full list of all 18 12 Hours to Die achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
Access debug mode
Access the Mafia Deleted Scene
Finish the game
Complete Chapter 6
Complete Chapter 5
Complete Chapter 4
Complete Chapter 3
Complete Chapter 2f
Complete Chapter 2e
Complete Chapter 2d
Solve Chapter 2d's Puzzle
Complete Chapter 2c
Solve Chapter 2c's Puzzle
Complete Chapter 2b
Solve Chapter 2b's Puzzle
Solve Chapter 2's puzzle
Complete Chapter 2
Complete Chapter 1