Recap: Justice League Unlimited S 2 E 11 Panic In The Sky
Generic Doomsday Villain: Lex Luthor figuratively got under Brainiac's skin after the latter literally got under his skin by accusing him of being one of these. Luthor pointed out that Brainiac had no real plans of doing anything with its vast store of knowledge and that it had no real reason for destroying the universe. Brainiac realized Luthor had a point and agreed to a Fusion Dance so they could actually do something with all of that power and knowledge.
The Reveal: Luthor isn't the one pulling the strings...Brainiac is.
Wham Episode: Big time. The Original Seven are together again and go on to confront Luthor without the rest of the league, and in the last seconds of the episode it's revealed that Brainiac has been implanted in Luthor and that he is the true Man Behind the Man.