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
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
Complete Chapter 2
Solve Chapter 2's puzzle
Complete Chapter 1
Access the Mafia Deleted Scene