Positive Man

Positive Man was originally a human scientist living on a different planet in the 31st Century who tried to destroy his own world using a massive bomb. In the explosion, he was turned into a gigantic force being made up of positively charged ions, while a lab animal was transformed into the Negative Creature. As Positive Man, he destroyed many worlds and the Legion of Super-Heroes failed to stop him. Finally, Supergirl lured the Negative Creature close to the Positive Man and the two were attracted and cancelled each other out. ("Supergirl's Greatest Challenge!")