I believe in the Narutoverse only a few days have actually passed, lol. The villain that has had the most impact up to this point would be a hard one between Kabuto and Obito, Obito summoned the Juubi but Kabuto revived Madara which is now the biggest threat alongside the rampaging Juubi.
The biggest hero would have to go to Itachi, without what he did, Naruto and the rest of his comrades would probably be near death or exhausted (6 Jins vs 4). Don't get me wrong, without Naruto and what he has currently done so far in the war things would be going pretty badly and the alliance probably would have lost by now or real soon.
That being said, Itachi, Naruto, Kabuto and Obito at the moment have made the biggest impact on the ongoing war.