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