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