His family might have neglected him in some ways. Naruto grew up alone and feeling unwanted in the original story. If in the fanfiction, his family was around but still didn't give him the love and attention he needed, it would be a valid reason for his anger. He has always craved connection and acceptance, and if his family failed to provide that, he would be furious.
He could also distance himself from them. Naruto might choose to avoid his family, not wanting to be around them as a way to show his anger. He could move out or stop participating in family activities.
It could be due to a misunderstanding. Perhaps someone spread false rumors about him, and as a result, people started treating him differently. He might be angry at everyone because he feels that no one bothered to find out the truth from him. Also, if there were some new rules or restrictions imposed on him without proper explanation, that could fuel his anger.
One possible reason could be that the Cullens make a decision about her future without consulting her. For example, if they decide she should leave Forks for her own safety without asking her how she feels about it.
One possible reason could be that Konoha has made decisions without considering Naruto's opinions. Maybe they have made policies that Naruto believes are unjust towards certain groups, like the treatment of the Uchiha clan in the past. Naruto, who values fairness and friendship, would be angry at such insensitivity from his village.
Perhaps Naruto has always felt different from others in the village. And when he finally learns about his parents, he realizes that their actions, even if they were for a good cause like protecting the village, still made his life very difficult. He might be angry that they didn't find a better way to handle things so that he didn't have to suffer so much growing up.
One common reason is Hermione's over - protectiveness. Sometimes she tries to control situations too much, which can make Harry feel suffocated and thus angry. For example, in some fanfictions, she might try to stop Harry from taking risks in a dangerous mission, which he sees as her not believing in his abilities.
One possible reason could be that Erza might have taken on a dangerous mission alone without informing Natsu. Natsu is protective of his friends and would get angry if he thought Erza was putting herself in unnecessary danger.
One possible reason could be that Harry has been spending too much time on his heroic duties and not enough time with Ginny. Another might be that he made a decision without consulting her, like taking on a particularly dangerous mission. It could also be something as simple as he forgot an important date or anniversary.
One possible reason could be misrepresentation of her character. In some fanfictions, authors might change her personality to fit a certain plot, like making her overly jealous or mean, which would be out of character for the gentle Hinata. This could make her seem unlikable and thus anger fans who love the original Hinata.
One possible reason could be that Tsunade makes a decision regarding the village that Naruto strongly disagrees with. For example, if she refuses to send help to a neighboring village in need, Naruto, with his strong sense of justice, might get angry. He's always been about protecting and helping others.