Here is the full list of all 32 Another Crab's Treasure achievements.
Shoot a crab with a gun.
Try on every shell in the game.
Defeated the Consortium.
Learn all adaptations.
Fall off a cliff.
Fully upgrade Kril's fork.
Get your shell back.
Defeated Firth.
Defeated Praya Dubia.
Defeated Camtscha (For real.)
Defeated Camtscha.
Find a certain hero's helmet.
Defeated Inkerton.
Unlock all skills on the Path of The Hermit.
Unlock all skills on the Path of The True Crab.
Defeated Petroch.
Defeated Roland.
Defeated Voltai.
Unlock all skills on the Path of The Predator.
Defeated the Ceviche Sisters.
Defeated the Scuttling Sludge Steamroller.
Defeated the Royal Shellsplitter.
Purchase some insurance.
Defeated Pagurus.
Defeated Topoda.
Defeated Heikea.
Defeated the Curdled Carbonara Connoisseur.
Defeated the Diseased Lichenthrope.
Start the treasure hunt.
Defeated Magista.
Defeated a miniboss.
Defeated Nephro.