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