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