Here is the full list of all 27 OVRDARK: a Do Not Open story achievements.
Sticks a dart in the bull's eye
Be within 1 meter of Michael in a chase and escape
Solve the final riddle without failing once
Arrives in the hall for the first time
Complete the statue of concord
Escape from the mortal room on the first try
Turn on the generator
Pick up the axe
Kill Michael Goreng
Complete the game without dying
Die for the first time
Collect Julia's 3 teddies
Escape from the death room
Complete the game for the first time
Complete the game without using save cassettes
Hit the bobblehead doll
Have a flashback
Hang up Lexa in the middle of a call
Solve the Siamese twins riddle
Solve the chess riddle in less than 20 moves
Get the gas mask
Solve the 3 frames riddle
Get Mike's research
Die in toxic zone
Smoke 5 cigars
Drink 5 energy drink cans
First meeting with Michael