Here is the full list of all 50 SLICE achievements.
You made your first Slice
Solved 5 Levels
Solved Level 9 Puzzle
Beat Light World 1
Solved 15 levels
Beat Dark World 1
Discovered Color Changer
Solved 25 Levels
Beat World 2
Solved Level 3 of Dark World 2
Solved Level 7 of Dark World 2
Solved 35 Levels
Solved Level 10 of Dark World 2
Beat Dark World 2
Discover Anti-Gravity Object
Solved 45 Leves
Solved Level 6 of World 3
Beat Light World 3
Solved 55 Levels
Solved Level 4 of Dark World 3
Beat Dark World 3
Discover Reversed Gravity
Solved 65 Levels
Beat Light World 4
Solved 75 Levels
Beat Dark World 4
Discovered Anti-Targets
85 Levels
Beat Light World 5
Solved 95 Levels
Beat Dark World 5
Finished The Game
You Sliced Objects 100 Times
Entered Solid Symmetry World
Completed Solid Symmetry World
Entered Lined Symmetry World
Completed Lined Symmetry World
Unlocked Sand World
Beat Sand Level 1
Beat Sand Level 2
Beat Sand Level 3
Beat Sand Level 4
Beat Yin-Yang World 1
Sand World Completed
Beat Yin-Yang World 2
Beat Yin-Yang World 3
Beat Yin-Yang World 4
Beat Yin-Yang World 5
Yin-Yang World Completed
Outsmarted the Hidden Target