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