Here is the full list of all 44 Nuclear Throne achievements. It takes around 200 hours to unlock all of the achievements on Windows.
Loop as every character.
Reach the Nuclear Throne in under 10 minutes as Plant.
Defeat Mom.
We hereby sincerely apologize.
Reach Level Ultra as any character.
Reach 7-3 on a Daily.
Die.
Reach 2-1.
Reach 3-1.
Reach 3-?.
Reach 6-1.
Reach 5-1.
Reach 5-?.
Loop past the Nuclear Throne.
Defeat Horror.
Reach the Nuclear Throne.
Reach 2-? as Eyes.
Unlock a Golden Weapon for every character.
Eat a Hyper Weapon as Robot.
Unlock a Crown as any character.
Unlock a Golden Weapon as any character.
Defeat Lil Hunter.
Defeat the Nuclear Throne.
Defeat Throne II.
Loop the game.
Defeat Big Dog.
Defeat Big Bandit.
Reach 4-? as Crystal.
Reach the Nuclear Throne with Melting without choosing Rhino Skin or Strong Spirit.
Defeat the Technomancer as Steroids.
Reach 2-1 on Hard Mode as Chicken.
Defeat Mom as Rebel.
Defeat Hyper Crystal as Horror.
Defeat Captain as Rogue.
Unlock a Golden Disc Gun or Golden Nuke Launcher.
Reach Level Ultra as Skeleton.
Play as Frog.
Sit on the Nuclear Throne as headless Chicken.
Defeat Hyper Crystal.
Defeat the Technomancer.
Unlock all Crowns as one character.
Unlock Hard Mode.
Defeat Captain.
Get 100% of the unlocks.