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