Here is the full list of all 20 One Last Time achievements.
Complete the Prologue.
Complete Stage 1.
Complete Stage 2.
Complete Stage 3.
Complete Stage 4.
Complete Stage 5.
Complete Stage 6.
Complete Stage 7.
Complete the Extra Stage.
Set off a trap for the first time.
Teleport for the first time.
Switch your player for the first time.
Pick up a key for the first time.
Complete a puzzle in less than 5 seconds.
Spend over 3 minutes on a puzzle.
Reset a single puzzle 5 times.
Complete a puzzle with the Puzzle Grid turned on.
Look at some Art.
Spend over a minute admiring Backgrounds.
Change Outfits.