Here is the full list of all 16 Cube Decider achievements.
Complete level 1
Complete level 10
Complete level 20
Complete level 30
Complete level 40
Complete level 50
Destroy 10 bushes
Have 2 buckets in your inventory at once
Have 2 keys in your inventory at once
Upgrade health to 11 points
Kill all enemies in the level
Die by fire
Extinguish 5 fires
Open 5 doors
Destroy 20 enemies with shields
Complete any bonus level