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