Full list of all 28 The Signifier achievements.
The base game contains 21 achievements, and there is 1 DLC pack containing 7 achievements.
Neutral ending with Laura
Get every impression available in the control panel
Nullify the mask to let the creature free
Solve the shame puzzle
Solve the password after seeing Johanna's room in reality
Solved the first perspective puzzle in the Dream Sequence
Found Martha's Room in Reality
Enter the repressed room
Solve Kitchen Puzzle
Found Laptop in the Objective State (Death Memory)
Solve one Raw Data
Give an incorrect password on purpose
Tell Tom that you don't know the password.
Solved the password gathering only information from the Childhood memory
Align with Go-AT
Align with the TSB
Try to dodge the tensions between Go-AT and the TSB
Try to damage Go-AT and the TSB by helping both
Good ending with Laura
Bad ending with Laura
Let the mask dominate over the creature