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.
Try on every shell in the game.
Find a certain hero's helmet.
Fully upgrade Kril's fork.
Defeated Inkerton.
Defeated Petroch.
Learn all adaptations.
Defeated Roland.
Defeated Voltai.
Unlock all skills on the Path of The Hermit.
Purchase some insurance.
Defeated Topoda.
Fall off a cliff.
Unlock all skills on the Path of The True Crab.
Defeated Heikea.
Unlock all skills on the Path of The Predator.
Defeated the Ceviche Sisters.
Defeated the Scuttling Sludge Steamroller.
Defeated the Consortium.
Defeated the Curdled Carbonara Connoisseur.
Defeated the Diseased Lichenthrope.
Defeated Pagurus.
Start the treasure hunt.
Defeated Magista.
Defeated a miniboss.
Defeated Nephro.
Defeated the Royal Shellsplitter.
Shoot a crab with a gun.