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