Naruto. He has the nine tails which seems to be the most powerful demon chakra wise, bar none (as far as we know), and he's learning certain techniques which are forcing him to improve his basics, including chakra control, chakra output, ect. His ninjutsu is going to be no joke, I have confidence that he'll be awesome at stealth things cuz he is a trickster. I'm just hoping his damn taijutsu doesn't stay so ugly. There's no doubt in my mind that naruto is going to learn a substantial number of techniques before the show ends, many of which most people would not be able to master, making naruto above average even without the demon chakra. However, as was stated before...he is the main character...