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