Here is the full list of all 12 Don't Forget Me achievements.
You have successfully completed your first memory tree. Congratulations!
You didn’t join the ranks of the Forgotten. Who knows what lies ahead for you now?
You hit the bullseye!
You changed your hair color.
You beat the one-armed-bandit!
Complete Ederel’s Hidden Memory section
Complete Pear’s Hidden Memory section
Complete Edward’s Hidden Memory section
You discovered what Alexandre was really up to
You discovered what Manuela was really up to
You finished Don't Forget Me
Bernard got back in touch with Pear and she saved you from Edward.