Dark Naruto

Dark Naruto is the manifestation of the dark side of Naruto Uzumaki, having been created from all the hatred that festered while the boy was ostracized and despised by the Hidden Leaf when Naruto was a child, purely due to the fact that Naruto harbored the Nine Tails or Kurama in his body which led to many villagers resenting or even hating him.

History
While training at the Falls of Truth to confront Kurama, Naruto is confronted by Dark Naruto as he explains he is while belittles Naruto on how quickly the people who used to hate changed their standing after Naruto saved them from Pain. From there, Naruto finds himself in a fight neither he nor his other self could win no matter how hard the either tried.

However, with Killer Bee's help, Naruto confronts his dark self once more and explains that while the Hidden villagers did hate him, he still trusted them as they were important to him and they gave him the confidence to live up to their eventual trust. This in turn weakens Dark Naruto as Naruto embraces him and thanked him for helping him become who is now. This causes Dark Naruto, accepting Naruto's ideals, to let go of his anger and fade away.

Trivia

 * The Road to Ninja Movie introduces a similar character named Menma, who is from an alternate continuity where he embraced Kurama and became evil.