Almost every antagonist in Naruto was defeated, killed, and stopped with "The Last Rasengan" hit.
So... who will it be? Obito? Madara? or Sasuke... ...
I still count Sasuke because he's obviously not 100% atm.
Sasuke. It'll be all cliche. They'll fight, almost be exhausted (Even though logically, Naruto can outlast Sasuke 3 times over), and then gather chakra for one last clash.