Professor Emil Hamilton is a fictional character in DC Comics' Superman titles. He is generally portrayed as a stereotypical absent-minded professor, with a gray beard and thick glasses and, at times, sort of a "Mr. Wizard" type character.
He has also theorized about how Superman's Kryptonian biology works, and deduced the best way to defeat villains based on analysis of their powers. He lost an arm during the Fall of Metropolis storyline, but replaced it with a self-designed cybernetic prosthesis.
Many years later, when John Henry Irons returned to Metropolis, just prior to the B13 Event, Hamilton felt he was being sidelined, as Superman now had access to a scientific genius who was also a fellow superhero. He disappeared during the B13 Event.
He eventually resurfaced as the Overmind, the leader of a cyberpunk gang plotting the return of Brainiac 13. He claimed, however, that the B13-technology in his prosthetic arm was controlling his actions. Presumably this claim held some truth, as he returned to his role as Superman's advisor using his innate understand of the futuristic technology now available to him.
Recently it was revealed that Hamilton was, in fact, the villain named Ruin, who had been targeting Clark Kent's loved ones. Ruin claimed to have discovered that Superman was sucking the sun dry of its solar energy, and that, in 4.5 billion years, it would mean the end of life on Earth. The identity of Ruin had been kept a mystery, until it seemed that Clark's friend, and former President of the United States, Pete Ross was Ruin. Pete Ross claimed innocence, but he became even more suspect when he escaped from custody. It turned out that it had been Hamilton who had framed Ross, and kidnapped him again from prison. Hamilton then confronted and revealed himself to Superman, seemingly killing the 5th dimension imp Mr. Mxyzptlk in the process when he tried to save Superman. Superman defeated the insane Hamilton, and saved Pete, Lana, and their child. Superman later cleared Ross' name and reputation, and Hamilton was apparently imprisoned.
Emil Hamilton is a normal human being and thus, has no inherent super powers, though he is a brilliant scientist and inventor. However, as Ruin he dons a "power suit." The suit allows Ruin to take advantage of his knowledge of Superman's weaknesses. From the suit powerful blasts of Kryptonian red sunlight can be fired, which essentially sap Superman of all his powers. Also, Ruin is able to transport himself to the Phantom Zone (though at a detriment to his health), and reemerge anywhere, effectively allowing him to teleport. If the suit is forcibly removed from Hamilton's body, it self-destructs with a massive force, apparently enough to destroy a small city, although enough time elapsed between the removal and the explosion for Superman to get it to a safe distance.
Emil has designed various prosthetic arms with unusual abilities, including one that acted as a sunscreen dispenser.
Returning in the later DC Animated Universe show Justice League Unlimited (now played by Robert Foxworth), Hamilton has secretly become a confederate of Amanda Waller, the leader of Project Cadmus. Hamilton uses cloning and other such methods to create metahumans loyal and subservient to Cadmus. Hamilton was their expert on genetics, along with the mental manipulatist Dr. Hugo Strange and splicing scientist Dr. Achilles Milo (later killed by Doomsday, after causing general mayhem through animal/human hybridization in prior DCAU series). It was discovered in the season one episode Fearful Symmetry that he had produced a clone of Supergirl through the genetic samples taken in Legacy. This sociopathic clone, code-named Galatea, would be of primary importance in the Cadmus Project's endeavors against the Justice League.
Superman finally discovers Hamilton's betrayal of trust in Season 2 of JLU. Hamilton is unrepentant of his actions, and makes it clear that he believes Superman can never be fully trusted again. This version of Hamilton has not been seen since the end of the 'Cadmus' story arc, when his chief contribution Galatea was defeated in battle.