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