Luthor was on the planet, wearing his warsuit at the time the explosion occurred -- because of this, he survived the explosion, as his warsuit protected him from the blast. The rest of the population wasn't as lucky though.
Luthor clung to a chunk of the exploded planet; and made a sculpture of his wife and son out of the rock. He was then rescued by one of Darkseid's Emissaries of Doom, who took him back to Earth, and he never seen his wife and son or any other Lexorian ever again.
Luthor blamed Superman for the death of his wife and son, and the entire Lexorian race. He was so filled with hatred that he couldn't even see passed that enough to realize that it was actually his fault they had all died.
- Issue # 544 (1983)
- Issue # 1 (1984)