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