Inverted Sunflower Star

Pycnopodia helianthoides (AKA Sunflower Star or Sun Starfish) is a nasty customer. This is the T. Rex of the starfish, and can travel a blistering 40 inches per minute to boot.
When you get one of these in a trap, it is imperative to remove them right away, or they will clamp down on whatever it is grabbing onto with up to 24 tube feet-filled arms with such force, it may be unable to extract the animal without ripping off some of the tube feet.
They also have pincers on their top side that are used to discourage potential predators. In addition, they can secrete a mild poison when agitated. In the ocean, it acts as a mild deterrent, but if this stuff is contained in a small tank, it could cause more serious damage to fish or other animals in such a constrained environment.
This is from the MBA Field Guide:

Juvenile sunflower stars start life with five arms—by maturity they sport up to 24 arms.
Most sea stars have a one-piece, semirigid skeleton. However, the sunflower star’s skeleton has a few disconnected pieces. They allow the sunstar’s mouth to open wide and its body to enlarge and take in big prey. A sunflower star can swallow an entire sea urchin, digest it internally and then expel the urchin’s test—its external shell.
In Monterey Bay, the sunflower star eats—in season—dead or dying squid. After the star digests the squid, the indigestible squid pen—its internal shell, which is too large to be defecated—works its way through the body wall.

I know of nothing that likes to eat Pycnopodia helianthoides, and I can see why. Besides the toxins, pincers, and enormous size (they grow over a meter long from tip to tip), they are covered in a viscous slime, much resembling a suit made of snot (it has the texture of grated yama imo).
It might be worth handling, just to give someone a hearty handshake immediately afterwards. I can just picture the look of horror on the hand of the recipient as they quickly withdraw from the shake, with tendrils of mucus stretching and extending like strings of natto linking the tips of a pair of chopsticks to a bed of freshly stirred fermented soy beans. Mmmmmm… Natto.