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