Like his heroic counterpart Batman, Owlman has no superpowers but possesses a keen, logical mind and is a brilliant inventor and martial artist. What makes him different from Batman, apart from his costume, is his complete lack of compassion. He literally doesn't care about anyone or anything, his actions spurred entirely by his dark sense of logic.
Owlman aided the Crime Syndicate in developing the Quantum Eigenstate Device: a quantum-powered nuclear bomb that possessed enough power to destroy the entire Earth. The Syndicate intended to use the QED to blackmail Earth's governments into surrendering what little power they had left, but Owlman had other ideas. Having conducted extensive research into parallel worlds, he came to the twisted realization that human choice had no meaning, that for every choice made there was another Earth out in the multiverse where the opposite choice had been made. Believing himself to be making the only logical choice, Owlman intended to take the QED to Earth Prime, a barren and lifeless Earth to which all other versions of Earth were connected. By detonating his device on Earth Prime, Owlman would destroy all other parallel Earths as well, completely annihilating all of reality.
When Owlman transported the QED to Earth Prime, Batman went after him after Johnny Quick was able to open a new portal to that world. Batman and Owlman fought but appeared to be evenly matched, though Batman lacked his evil counterpart's killer instinct. Fortunately, Batman was able to use Owlman's quantum teleporter device to transport both Owlman and the QED to another Earth, this one another wasteland devoid of life. When the QED detonated, only that one Earth was destroyed and Owlman was its only victim.