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.
Find a certain hero's helmet.
Fully upgrade Kril's fork.
Defeated Praya Dubia.
Defeated Camtscha.
Defeated Camtscha (For real.)
Defeated Inkerton.
Defeated Petroch.
Learn all adaptations.
Defeated Roland.
Unlock all skills on the Path of The True Crab.
Defeated Voltai.
Unlock all skills on the Path of The Hermit.
Defeated Pagurus.
Defeated Topoda.
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.
Purchase some insurance.
Start the treasure hunt.
Fall off a cliff.
Defeated Magista.
Defeated a miniboss.
Defeated Nephro.
Defeated the Royal Shellsplitter.
Shoot a crab with a gun.