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