Terra-man in the animated series. Don't get me wrong, he was one of the coolest villains on the show. I can understand him going after Abel when he was told that Abel created the Imperiex technology. But why would he continue to go after him after the Legion got in the way? Considering how powerful the Legion (and Kell-El) were, why not team up and try to take down Imperiex directly?
His mission was to stop Imperiex from ever existing. Taking out the villain himself wouldn't undo all the destruction he caused back in the future.