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