Ultimately you want all of them, but I went with Villain since the Villain/Conqueror combo is what forces your opponent to kill everyone else (or at least a couple of them) before they can kill Darth Revan.
I actually think Lord of the Sith is his least important zeta - it only protects you against TM drain. That's certainly good, but presumably your main goal is to beat JKR teams, and the only TM drain on that squad is GM Yoda's special. LOTS is mainly going to protect you from CLS/Han/Chewie teams, which I'd rate as a secondary concern.
