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