Sasuke obtained new power to supress even the Kyuubi chakra. First hinted by Kabuto in Part 1, this power stem from the Uchiha clan! Is this the reason Itachi let Sasuke live? What is this fearsome power? What is this scary Sharingan he used to attack Sai? My thoughts: I think the Uchiha blood is an inheritance from the ancient gods. Hence Itachi's words: "Only another with Uchiha blood could beat me". Hence Kakashi: "The true power of the clan...the terrifying Uchiha blood". That's why the MS jutsu have names like the gods who created the world. So maybe Uchiha Sasuke would be able to make the Death God retreat.