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