Superman: Last Stand of New Krypton (2010) #1

Plot

After Zod's first strike on Brainiac's ship proves useless, Kal-El uses a more tactical maneuver to enter it. Meanwhile, on New Krypton, Supergirl is joined in the fight against Brainiac's probe bots by Superboy, Mon-El, and the Legion of Super-Heroes. After taking control of the situation, Zod sends Mon-El and Supergirl back out into the fight, but has Superboy and the Legion arrested. Back in Brainiac's ship, Superman finds himself confronted not only by Brainiac, but by Luthor too.

Story continues in Supergirl (DC, 2005 series) #51. Luthor revealed as a robot in issue #3.