I would have to say the introduction of the 6 Paths of Pain. Especially his fight with Jiraiya. And the anime made it so much more epic! Just with the 6 paths standing before him with that eeree chanting soundtrack (gerei) playing in the backround just made it THAT much more bada$$. And I can't forget his soloing of the Leaf using Grand Almighty Push (chou shinra tensei) and Planetary Devastation (chibaku tensei). Of course he DID get trolled pretty hard in the Naruto fight AND during his Reanimation. . . -_-
Secondly, The revival of the Ten Tails. The fact that he tanked a TBB of that magnitude without a scratch and them preceeded to SPEEDBLITZ AND BITCHSLAP the likes of TAILED BEAST NARUTO was just purely EPIC! Ant also, The Ten Tails' Tailed Beast Bomb in form 2. It LITERALLY broke the cloud line and possibly even broke through the atmosphere itself! All that went through my head at that time was *Everyone is COMPLETELY F**KED!!!*
And lastly, I would have to say Madara's revelation of the Perfect Susano'o. The fact that there was another stage AFTER Final Susano'o just blew my mind! And its power was simply put *WHAT THE FLYING F**K* It was one of the craziest things I've ever seen.
As an honorable mention, I have to take it back to part 1 with a tie between Kimimaro Kaguya and Monkey King Enma. I loved the SH*T out of both of them!
But yeah. . . Those are my thoughts on the matter.