Ultimate Man is a villain who attempted to take over the world. His true identity is unknown; all that is known is that he was a scientist working alone in an observatory on a mountaintop, who, out of admiration for Superman's feats, decided to make himself into a superhuman by blasting himself with intense Cosmic Rays, causing his body to mutate at accelerated ways, thus simulating the effect of human evolution over billions of years upon his body.
The transformation granted him amazing superpowers, which he used to make mental contact with all the people of the world at once. He announced to them his superiority, but was quickly challenged by Superman, his former idol.
Superman was able to focus Ultimate Man's cosmic rays on him so intensely, that they evolved him into an ape-like figure.