Here is the full list of all 36 Super Meat Boy Forever achievements.
Beat The Other Side Light World without dying
Unlock Mega Bandage
Beat The Lab Light World without dying
Beat Tetanus City LIght World without dying
Beat The Clinic Light World without dying
Beat Every Warp Zone
Beat Chipper Grove Light World without dying
Beat Omega Alpha
Beat Dr Fetus
Punch 1000 things
Beat The Lab Guardian
Unlock Prototype Boy
Beat Manic
Find 1 Pacifier
Beat Big Slugger
Find 1 Warp Zone
Beat 0xDEADBEEF
Beat 0xDEADBEEF without dying
Beat Chipper Grove Dark World without dying
Beat The Clinic Dark World without dying
Beat Tetanus City Dark World without dying
Beat The Lab Dark World without dying
Beat The Other Side Dark World without dying
Unlock Brownie
Unlock Lil' Meat
Unlock Squirrel
Beat the game completely
Unlock Manic
Unlock Meatsona
Unlock Tofu Boy
Unlock Classic Boy and Classic Girl
Unlock MZero
Beat the game on New Game Plus
Unlock Dr. Fetus
Unlock Classic Dr. Fetus
Unlock the ultimate couple