Enraged over the death of his wife, Superman hunts down Brainiac with the intention of killing him, however, the Justice League, together with Lex Luthor, attempt to stop the hero before he crosses the line that he himself held strong for his entire career.
When Superman apparently succeds in killing Brainiac. Superman auto exiles himself. After Superman flees, Lex Luthor discovers that Superman didn't actually kill Brainiac, he only destroyed a robot clone. At Lois Lane's funeral, Lex Luthor decides to help the heroes after seeing Lois' death and Superman's most human side.
"From the moment I first saw him, I knew that...alien...was going to be my enemy. Yes, we both said we wanted to protect Metropolis, and of course the world, from harm...but he portrayed himself with an air of inexplicable selflessness that contradicted the reality of how I knew the world worked. Therefore, I knew this creature from another world had to have ulterior motives in coming to Earth. And though through all the ensuing years I could not find proof of his duplicity...I still knew he had to be defeated and destroyed. But now that I finally got what I have for so long desired...why am I not pleased?" — Lex Luthor