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