Well, it could show that their relationship was based on false pretenses. Harry might find out that Dumbledore had ulterior motives for taking him under his wing. In the fanfiction, this would completely change the dynamic. Instead of the warm, if somewhat distant, relationship in the books, it could be a relationship where Harry feels used and deceived. This new view of the relationship would likely drive Harry to break away from Dumbledore's influence and forge his own path more determinedly.
The relationship would become very strained. Harry's rejection would likely make Dumbledore re - evaluate his actions and how he has interacted with Harry. Dumbledore might be shocked at first, since he probably thought Harry was on the same page as him most of the time.
As the story progresses, Dumbledore might try to make amends. He could start revealing some of his secrets to Harry in an attempt to regain his trust. Harry, on the other hand, would be hesitant at first but gradually start to listen and understand Dumbledore's reasons.
The power dynamic also shifts. Usually, Dumbledore is seen as a mentor and a figure of authority. But when Harry denounces him, Harry is challenging that authority. In some fanfic, this could lead to a power struggle within the wizarding community as others take sides. It can also cause Harry to seek new allies who share his view of Dumbledore, changing the social fabric of the story.
The relationship turns into one of opposition in some fanfics. Harry, now independent, may be working towards goals that Dumbledore doesn't approve of. Dumbledore may see Harry as a loose cannon and try to control him from a distance, while Harry resents any such attempts. Their interactions become tense and full of unspoken accusations.
The fanfiction might show a more adversarial relationship. Harry could start to oppose Dumbledore's plans instead of following them blindly. This is very different from the original where Harry was mostly compliant. For example, in the original, Harry accepted Dumbledore's tasks like finding the Horcruxes, but in the fanfiction, he might question the motives behind these tasks and resist them.
It could create a rift. Harry might feel betrayed or not understood by Dumbledore. If Harry is starting to explore his own identity and Dumbledore is against it, Harry would likely be hurt and this could lead to a strained relationship. He might start to question Dumbledore's wisdom and guidance that he has always relied on.
Dumbledore, as Harry's guardian in the fanfiction, would probably use his influence in the wizarding world. He could make sure that Harry is taught by the best teachers at Hogwarts. He'd also be there to offer advice and guidance, especially when Harry faces challenges like dealing with Voldemort or other dark forces. For example, he might teach Harry some advanced defensive magic privately to better protect himself.
Some fanfictions might explore a more nuanced past relationship between them. Maybe they had interactions in their younger days that shaped their future enmity. Dumbledore, with his deep understanding of magic and people, could have recognized the darkness growing in Voldemort early on and tried to guide him away from it, but Voldemort's pride and thirst for power made him reject any such guidance.
Among the students, Harry's action would make him a very polarizing figure. Some students would see him as a hero for taking a stand against the all - powerful Dumbledore, while others would view him as a troublemaker. This would completely change the social dynamics within the school. The younger students might look up to him with a mix of awe and fear, while the older students might be more critical of his actions.
One possible reason could be Dumbledore's over - reliance on his own grand plan. He might have been so focused on the big picture of defeating Voldemort that he overlooked Harry's individual emotional and psychological needs. For example, Harry constantly had to face dangerous situations alone, and Dumbledore didn't always step in to protect him directly. This could have led to Harry feeling abandoned and having to grow up too fast without proper guidance in some aspects.