666 is a villain from the DC comics - his name is inspired by the Satanic symbol.
666 was a vigilante that fought with the Magog generation of superheroes up until the events that took place in Kingdom Come. He had no interest in reformation when Superman returned from his exile to force the new generation of superheroes to join the Justice League voluntarily, so he and a few other meta-humans were instead incarcerated at the Gulag Superman and the Justice League constructed to contain and re-educate them. After a while 666 and the meta-humans started revolting and killed the warden Captain Comet. They engaged the Justice League in an all-out battle. Captain Marvel then used his lightning to break open the facility. 666 died when the bomb dropped by the Blackhawk Squadron to destroy most of the meta-humans had been prematurely detonated by Captain Marvel.