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