Vril Dox (Earth-Prime)

"This is why we need you! You took down Brainiac when you were only a teenager."

- Impulse to Clark Kent

Brainiac is an enemy of the Legion of Super-Heroes and a former enemy of Superman.

Enemy of Superman
Brainiac was born on the planet Colu, but eventually left and travelled to Earth, where he fought and was defeated by Superman.

Future
At some point in the future, Brainiac became an enemy of the Legion of Super-Heroes, and was the main cause of Winn Schott travelling to the thirty-first century.