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