Here is the full list of all 77 Crab Champions achievements.
Deal over 100K damage in a single shot
Defeat a boss without taking any damage
Defeat a boss in under 10 seconds
Defeat an elite without taking any damage
Fill all mod and perk slots in your inventory during a single run
Get a win on any difficulty
Get a win on Nightmare difficulty
Get 5 wins total on Nightmare difficulty
Get 3 wins in a row on any difficulty
Get 2 wins in a row on Nightmare difficulty
Get 5 wins in a row on Nightmare difficulty
Get a win after looping at least once
Get a win on Normal difficulty without taking any damage
Get a win on Normal difficulty with 5 or less shop purchases
Get a win with over 1M unspent crystals in your inventory
Get a win with over 10000 eliminations
Get a win without firing your weapon
Clear island 25 in 20 minutes or less
Clear island 50 in 40 minutes or less
Clear island 100 in 60 minutes or less
Get 10000 max health on a single run
Fill 20 weapon mod slots with legendary weapon mods
Defeat a boss with at least 5 greed perks in your inventory
Level up a mod or perk to level 20 in a single run
Salvage 100 pickups in a single run
Make 100 purchases at shops in a single run
Reroll shops 50 times in a single run
Destroy 25 totems in a single run
Clear the first biome on Nightmare difficulty without taking any damage
Survive until island 100
Get a win with the Auto Rifle on any difficulty
Get a win with the Auto Rifle on Nightmare difficulty
Get a win with the Dual Shotguns on any difficulty
Get a win with the Dual Shotguns on Nightmare difficulty
Get a win with the Dual Pistols on any difficulty
Get a win with the Dual Pistols on Nightmare difficulty
Get a win with the Auto Shotgun on any difficulty
Get a win with the Auto Shotgun on Nightmare difficulty
Get a win with the Burst Pistol on any difficulty
Get a win with the Burst Pistol on Nightmare difficulty
Get a win with the Sniper on any difficulty
Get a win with the Sniper on Nightmare difficulty
Get a win with the Crossbow on any difficulty
Get a win with the Crossbow on Nightmare difficulty
Get a win with the Orb Launcher on any difficulty
Get a win with the Orb Launcher on Nightmare difficulty
Get a win with the Rocket Launcher on any difficulty
Get a win with the Rocket Launcher on Nightmare difficulty
Get a win with the Minigun on any difficulty
Get a win with the Minigun on Nightmare difficulty
Get a win with the Blade Launcher on any difficulty
Get a win with the Blade Launcher on Nightmare difficulty
Get a win with the Cluster Launcher on any difficulty
Get a win with the Cluster Launcher on Nightmare difficulty
Get a win with all weapons in the game
Complete all challenges
Get a win on any difficulty with 5 or more difficulty modifiers active
Get a win on any difficulty with all difficulty modifiers active
Get a win on Nightmare difficulty with all difficulty modifiers active
Get a win with the Flamethrower on any difficulty
Get a win with the Flamethrower on Nightmare difficulty
Get a win with the Arcane Wand on any difficulty
Get a win with the Arcane Wand on Nightmare difficulty
Get a win with the Laser Cannons on any difficulty
Get a win with the Laser Cannons on Nightmare difficulty
Get a win with the Seagle on any difficulty
Get a win with the Seagle on Nightmare difficulty
Get a score of at least 300 in the Arcade minigame
Get a score of at least 50 in the Holdout minigame
Reach Silver account rank
Reach Gold account rank
Reach Sapphire account rank
Reach Emerald account rank
Reach Ruby account rank
Reach Diamond account rank
Get a win with the Marksman Rifle on any difficulty
Get a win with the Marksman Rifle on Nightmare difficulty