Perhaps in this fanfiction, Naruto discovers some dark secrets about the village. Secrets that make him feel like he's been used all along. Like the village was only using him as a weapon against their enemies. This realization could make him resent everyone in the village, thus hating everyone.
Well, it could be that Percy has had some really bad experiences in his life that made him bitter towards everyone. Maybe he was betrayed by friends in the past, so now he just can't bring himself to trust or like anyone.
Maybe Harry has had some really bad experiences that made him bitter towards everyone. For example, he could have been betrayed by his friends multiple times.
Perhaps the plot could revolve around a magical accident or curse that makes Harry lose his ability to feel positive emotions towards others. As a result, he starts to hate everyone. He begins to act out against the people he once cared about, causing chaos in Hogwarts and the wider wizarding community. His friends would be shocked and try to find a way to reverse the effect, but Harry would resist their attempts.
Perhaps Harry has seen the worst in people too often. He might have witnessed so much greed, envy, and cruelty among those around him that he has lost all faith in humanity and thus hates everyone. He could be in a situation where he feels completely alone and that no one truly understands him.
One possible plot could be that Naruto discovers that his friends have been keeping secrets from him that make him feel betrayed. For example, they might have made a deal with the village elders that goes against Naruto's values. This would break his heart as he thought they were all in it together. Another idea is that the villagers, who he has tried so hard to protect and earn the respect of, suddenly turn on him due to false rumors spread about him.
Well, one possibility is that Naruto is framed for a serious crime he didn't commit. Maybe someone fakes evidence that he's been working with the enemies of the village. His friends, believing the false evidence, turn their backs on him. He then has to fight not only against the village's distrust but also to clear his name and find out who really set him up.
Well, it could show Naruto being shunned by the village too. Since everyone thinks he has cheated in some way. His teachers might stop believing in him. The plot could revolve around Naruto's journey to prove his innocence. He might have to go on a solo mission to find evidence that clears his name, all while dealing with the emotional pain of being cheated on by those he trusted.
The plot could be that Naruto discovers a dark secret about his family that makes everyone in the village fear and reject him. For example, if it was thought that his father was responsible for a great tragedy. Naruto would then struggle to come to terms with this new information while also trying to regain the trust of those around him. He might find allies in unexpected places, like some of the outcast ninja from other villages.
Well, it could be that Naruto has been betrayed too many times. Maybe he discovers that some of his closest friends have been using him all along for their own gains. So he starts to hate everyone, and the story could be about his journey of isolation and self - discovery as he tries to come to terms with his new feelings.
Maybe a new, powerful and evil ninja from another land. This ninja could have come to the village and caused a lot of chaos, making Naruto believe that no one in his village was capable of protecting themselves or him. So he blames everyone for their weakness and starts to hate them all, with this new ninja being the root of the problem.