Here is the full list of all 32 Deadlings: Rotten Edition achievements.
Complete phase 2.
Finish 20 levels without killing a single zombie.
Kill the zombie with the other zombie.
Collect 50 stars.
Discover a deadly lasers.
Unlock the Lazybrain.
Complete phase 1.
Collect 800 brains.
Kill over 100 zombies.
Collect 400 brains.
Collect 150 brains.
Unlock the Gasfat.
Complete level 04 using one zombie.
Unlock the Creep.
Complete phase 3.
Complete phase 4.
Discover an awesome portals!
Discover a freezing freezers.
Discover a crazy mutators.
Complete all levels in Nightmare Mode with maximum rank.
Complete 5 levels in Nightmare Mode.
Complete 20 levels in Nightmare Mode.
Complete 45 levels in Nightmare Mode.
Complete 60 levels in Nightmare Mode.
Collect 100 stars.
Collect 150 stars.
Collect 200 stars.
Complete all levels in Normal Mode with maximum rank.
Complete level 14 in less than 10 seconds.
Complete all bonus levels.
Complete all bonus levels with maximum rank.
Complete bonus level 10.