Here is the full list of all 32 Another Crab's Treasure achievements.
Try on every shell in the game.
Learn all adaptations.
Find a certain hero's helmet.
Shoot a crab with a gun.
Defeated the Consortium.
Defeated the Curdled Carbonara Connoisseur.
Get your shell back.
Defeated Firth.
Defeated Praya Dubia.
Defeated Camtscha (For real.)
Defeated Camtscha.
Fully upgrade Kril's fork.
Defeated Inkerton.
Defeated Petroch.
Defeated Roland.
Unlock all skills on the Path of The Hermit.
Defeated Voltai.
Defeated the Ceviche Sisters.
Unlock all skills on the Path of The Predator.
Defeated the Scuttling Sludge Steamroller.
Unlock all skills on the Path of The True Crab.
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.