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.
Reach Level Ultra as Skeleton.
Play as Frog.
Unlock a Golden Disc Gun or Golden Nuke Launcher.
Sit on the Nuclear Throne as headless Chicken.
Defeat the Technomancer as Steroids.
Defeat Hyper Crystal as Horror.
Loop as every character.
Defeat Captain.
Defeat Captain as Rogue.
Reach the Nuclear Throne in under 10 minutes as Plant.
Eat a Hyper Weapon as Robot.
Reach 2-1 on Hard Mode as Chicken.
Reach 4-? as Crystal.
Unlock Hard Mode.
Defeat the Technomancer.
Defeat Mom as Rebel.
Unlock a Golden Weapon for every character.
Defeat Hyper Crystal.
Reach the Nuclear Throne.
Unlock a Crown as any character.
Defeat Mom.
Reach 5-?.
Defeat Horror.
Reach 7-3 on a Daily.
Reach the Nuclear Throne with Melting without choosing Rhino Skin or Strong Spirit.
We hereby sincerely apologize.
Reach Level Ultra as any character.
Loop past the Nuclear Throne.
Defeat Throne II.
Unlock a Golden Weapon as any character.
Reach 2-? as Eyes.
Loop the game.
Defeat the Nuclear Throne.
Reach 6-1.
Defeat Lil Hunter.
Reach 3-?.
Reach 5-1.
Die.
Reach 3-1.
Reach 2-1.
Defeat Big Dog.
Defeat Big Bandit.