Here is the full list of all 20 Rabisco achievements.
The base game contains 18 achievements, and there is 1 DLC pack containing 2 achievements.
You gave your first steps!
You finished the Grey World!
You finished the Blue World!
You finished the Green World!
You finished the Beige World!
You finished the Yellow World!
You finished the Orange World!
You finished the Pink World!
You finished the Purple World!
You finished the Dark Blue World!
You found all moon's stars!
You found all paint bukects!
You found all gems!
You found the hidden room!
You cleared yourself in the white paint pool!
You literally found easter eggs!
Grab the rainbow star in the first level.
You defeated the slime boss!
You activated the hard mode (no checkpoints)!