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