Here is the full list of all 14 BiT Evolution achievements.
Complete 20 levels in the game's challenge mode
Collect all of the pixels in the game
Defeat the game's final boss
Defeat the boss of World 4
Defeat the boss of World 3
Carry the first Spider Clam to the goal tape on level 3-11
Defeat the boss of World 2
Complete a level without ever entering the Realm of Code
Defeat the boss of World 1
Find any hidden area within the game
Obtain a gold star on any 10 levels
Survive 30 seconds with the "death wall" in level 1-11
Obtain a gold star on any level
Complete a level without killing any enemies (not even bats!)