Using the specifications you used ex: " adding to the plot, etc."
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7. Naruto -- the titular character, another driving force for Sasuke to get stronger, his counterpart & one of the children of prophecy.
6. Hagoromo. While it's true we didn't get much from him, his ball sack is literally the whole reason we read this story for 15 years.
5. Itasama driving motivation for Sasuke through out majority of the story, gave Naruto advice in the war, without it Im sure Naruto would have died.
4. Obito, he literally dragged this Manga along into war, while having an air of mystery & a haxxed ass ability.
3. Madara -- naturally powerful, the epitome of a villain, complex in his own right.
2. BZ honestly without him there would be no plot, think of all the history he's witnessed
1. Sasukesama, lololol Kishimoto says more than enough about Sasuke as to why he's #1