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