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