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