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