Clearly Kishimoto is the most powerful in the NV, because his ability to suppress the powers of those we've considered god-tier throughout the series is unmatched. We have many examples, including the main character (depending on who you talk to of course). Here are some examples of those you could argue was really tempered down for plot progession....
1) Obito Uchiha (If this guy kept his ability to use his MS powers while being the Jubi-Jin, I see no concievable way for Naruto/Sasuke to take him down. Even without it, he had the both of them outclassed for the majority of the fight.)
2) Madara Uchiha (In terms of raw ability, there's really no one like him outside of Hashirama. However, once he became the Jubi-Jin he became an uncontrollable monster who even found pleasure in getting batted around by an Eight-Gates Guy. In addition, we never really got to see his full ability with his dual Rinnegan. It wasn't long after 'til he got stabbed by BZ, which by the way was also utter nonsense, given his sensory skill. Maybe I'm missing something, but this is coming from the same guy who used ordinary senjutsu to dodge Sasuke's sword strikes without eyes. Also, he didn't utilise the Six Paths Technique much.)
3) Naruto Uzumaki (Somewhat bouncing off another thread in this forum, Naruto's full ability to this day hasn't been explored greatly. I mean, this guy had/has, depending on who you ask, all the TB's chakra including a full Kurama. I would've loved to see him shoot lava balls out of his mouth, use Suiton, etc...instead the same ole' Shadow Clones, Rasengan and it's many variants. A guy with as much chakra as he does, is capable of sooo much more and leaves a lot to desired. Excluding the TB's, I could make the same case for Minato.)
4) Nagato (Simple. Mobility. Though he didn't awaken the Rinnegan naturally, he mastered it to the point, he was called the Third Six Paths. If he could move properly he'd be a hassle for even the strongest of shinobi.)
5) Orochimaru (He lost both his arms in Part 1, and all we saw him really do with them in tact was the Reanimation and a couple elemental techs during the real Chūnin Exams. I've always been curious about his full arsenal.)
Of these five, who was the most boggled down in your view? If you have others, feel free to let loose.