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