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