Here is the full list of all 43 Kill Yourself achievements.
Solve the corresponding ending
Read all the book entries
Complete the tutorial
Watch the credits til the end
Bump your head in a non-lethal manner
Find the secret letters
Make a flamethrower
Walk 100 meters
Walk 500 meters
Walk 1500 meters
Walk 5 kilometers
Rip and burn the necktie
Kill all living things in a single game
Repeat at least one death