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