Nuclear Throne hosts 44 different achievments covering all major parts of the game. As such, most achievments are tied to progress such as unlocks and killing bosses.

Because of the simplicity of many achievments there will not be in-depth guides for every single one, for progression one can follow along with the Survival Guide(link later) and for B-Skins one can find advice on their specific character pages.

There are 5 achievments in the game that are particularly difficult or enough on the technical side to warrant guides, they are as follows:

Color Legend:
Low skill | Intermediate skill | Professional skill | Master skill

Characters B-Skins
Eyes Unlocked Reach 2-1. Fish Can Roll Loop as every character.
Melting Unlocked Die. Crystal Can Shield Reach 4-? as Crystal.
Plant Unlocked Reach 3-1. MMMMMMHMMM! Reach 2-? as Eyes.
Y.V. Unlocked Reach 3-?. Everything Hurts Reach the Nuclear Throne with Melting without choosing Rhino Skin or Strong Spirit
Robot Unlocked Reach 5-1. Blood Blood Blood Reach the Nuclear Throne in under 10 minutes as Plant.
Chicken Unlocked Reach 5-?. Verified Unlock a Golden Weapon for every character.
Steroids Unlocked Reach 6-1. 6e 69 63 65 Eat a Hyper Weapon as Robot.
Rebel Unlocked Loop past the Nuclear Throne. Way Of The Chicken Reach 2-1 on Hard Mode as Chicken.
Horror Unlocked Defeat Horror. Science Defeat the Technomancer as Steroids.
Rogue Unlocked Reach the Nuclear Throne. Forget The Old Days Defeat Mom as Rebel.
Frog Zone Play as Frog.
Thriller Defeat Hyper Crystal as Horror.
Unstoppable Reach Level Ultra as Skeleton.
Never Look Back Defeat Captain as Rogue.
Preloop Bosses Loop Bosses
Bandit Stopper Defeat Big Bandit. Advanced Sitter Defeat Throne II.
Dog Owner Defeat Big Dog. Frog Slayer Defeat Mom.
Hunter Killer Defeat Lil Hunter. Crystal Smasher Defeat Hyper Crystal.
Throne Sitter Defeat the Nuclear Throne. Techno Killer Defeat the Technomancer.
The Struggle Is Over Defeat Captain.
Progression Unlocks
Not Bad Reach 7-3 on a Daily. Good Find Unlock a Golden Weapon as any character.
The Struggle Continues Loop the game. Good Riddance Unlock the Golden Disc Gun or Golden Nuke Launcher.
Ultra Time Reach Level Ultra as any character. Crown Life Unlock a Crown as any character.
Go Hard Unlock Hard Mode. Vault Raider Unlock all Crowns as one character.ul
Ultra Mutant Get 100% of the unlocks.
Sincere Apologies. We hereby sincerely apologize. Impossible Sit on the Nuclear Throne as headless Chicken.
Die to a Disc Gun. Defeat the Throne, then become headless to its death explosions and Thronesit.