Here is the full list of all 32 Another Crab's Treasure achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Defeated Nephro.
Defeated Magista.
Defeated a miniboss.
Defeated the Diseased Lichenthrope.
Defeated Heikea.
Defeated Topoda.
Defeated the Consortium.
Defeated Pagurus.
Defeated Voltai.
Defeated Roland.
Defeated Petroch.
Defeated Inkerton.
Defeated Camtscha.
Defeated Firth.
Defeated Camtscha (For real.)
Unlock all skills on the Path of The True Crab.
Unlock all skills on the Path of The Predator.
Unlock all skills on the Path of The Hermit.
Fully upgrade Kril's fork.
Purchase some insurance.
Fall off a cliff.
Shoot a crab with a gun.
Start the treasure hunt.
Defeated the Royal Shellsplitter.
Defeated the Curdled Carbonara Connoisseur.
Defeated the Scuttling Sludge Steamroller.
Get your shell back.
Defeated the Ceviche Sisters.
Find a certain hero's helmet.
Try on every shell in the game.
Learn all adaptations.
Defeated Praya Dubia.