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