Here is the full list of all 21 Slip achievements.
Turn off your toaster.
Beat the first boss.
Beat any level without dying and collecting all powercubes.
Beat any level without dying.
Earn a score of 100,000 or more in a single level.
Collect 100 powercubes in a single level.
Earn a speed bonus in any level.
Beat the second boss.
Beat the third boss.
Earn a score of 200,000 or more in a single level.
Earn a score of 300,000 or more in a single level.
Earn a score of 400,000 or more in a single level.
Earn 25% star completion.
Earn 50% star completion.
Earn 75% star completion.
Earn 100% star completion.
Enter 2 Hypercubes in a single level.
Hit 9 checkpoints in a row without dying.
Clear all the challenge levels on any difficulty.
Collect 10000 Powercubes.
Beat the final level with the "Steve's Bane" unlock equipped.