Source: DC Universe
Location: Outer Space
Threat Assessment: 8. Pretty nasty fella. Looking like a huge starfish, Starro can exist in outer space. He can regenerate from practically nothing. He is full of energy, EVIL energy of course, and can shoot out beams of energy. Worse, he creates little versions of himself that latch onto your face making you a thrall of Starro.
Limitations: Originally lime, the dust not the fruit, brought him down. Salt was also sometimes used. Mostly though you need a few superheroes and a lot of luck.