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