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