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