It could lead to a lot of conflict. His friends might try to reason with him, but if he's too angry, he might push them away. This could split their group apart, creating new alliances or just leaving Harry isolated for a while. His anger can also attract the attention of the wrong sort of people, like those who want to use his emotional state for their own gain.
Ginny's anger could make Harry realize his mistakes and try to make amends. This might strengthen their relationship in the long run as they work through their issues. However, in the short term, there could be a lot of tension and arguments. Ginny might also start to question whether Harry is really the right person for her, and Harry could start to feel insecure about their relationship.
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.
Their relationship could become strained. Ginny might start to question her love for Harry. In some fanfics, she could even consider leaving him. This would put a lot of pressure on Harry to fix things and make amends.
Well, it could create a lot of tension. If Harry ignores everyone, it might lead to misunderstandings. His friends might feel left out or hurt, which could drive a wedge in their relationships. This in turn can change the whole dynamic of the group. For example, they might not be as united when facing challenges, and it could also lead to some of them trying to figure out why Harry is acting this way, adding a mystery element to the plot.
It can create a lot of tension. For instance, Harry might start to act independently, which could lead to unforeseen consequences. He could go off on his own missions, putting himself in more danger than if he were with the Order.
It changes his perception quite a bit. Usually, Harry is seen as a hero. But in this fanfiction, he becomes a victim of false judgment. This makes him more relatable in a way, as we all have felt wronged at some point. It shows his vulnerability and how he might handle being in a tough situation where no one believes him.
He might lash out with his magic. For example, he could send a spell flying at the source of his anger without really thinking. Sometimes, he just glares intensely, his green eyes filled with fury. And he may raise his voice, shouting at those who have angered him.
His anger could drive him to take risks he wouldn't normally take. Maybe he decides to go after a powerful enemy on his own without proper backup because he's so angry that he doesn't think clearly. This could put him in great danger and also change the course of the story as the other characters then have to scramble to save him.
In some fanfictions, Harry might use his knowledge of magic in unexpected ways. For example, he could combine spells in a new and creative manner that others haven't thought of. This gives him an edge over everyone.
He might be confused at first. Harry isn't always the quickest to understand Hermione's motives right away. So he could just stand there, looking at her with a puzzled expression on his face, not really knowing what he did wrong.