Here is the full list of all 27 HackyZack achievements.
100% the game.
Clear all of W6 target levels.
Beat all Target level Normal times.
Beat all Target level Dev times.
Clear all of W5 target levels.
Clear all of W4 target levels.
Unlock Leroy as a Playable Character.
Clear all of W3 Target Levels.
Clear all of W2 target levels.
Clear all of W1 target levels.
Complete all levels in World 6.
Collect all stickers in W6.
Complete all levels in World 5.
Unlock Kelly as a playable character.
Collect all stickers in W5.
Unlock Shadow as a playable character.
Collect all stickers in W3.
Collect all stickers in W2.
Unlock Fara as a playable character.
Collect all stickers in W1.
Unlock Fell as a playable character.
Collect all stickers in W4.
Complete all levels in World 4.
Complete all levels in World 3.
Unlock Frog as a playable character.
Complete all levels in World 2.
Complete all levels in World 1.