It could lead to a rift between Harry and Dumbledore. Their relationship might become strained, and this could affect the unity and cooperation within the wizarding community. For example, other characters might take sides, causing division.
One possible consequence is that Harry could put himself in danger. Dumbledore is usually very wise, and his advice is often meant to protect Harry. By not listening, Harry may walk into a trap or face a more difficult situation than he expected.
There's also a chance that Harry's refusal to listen could lead to unexpected positive outcomes. He might discover a new way of doing things that Dumbledore hadn't considered. However, this is very risky as Dumbledore's experience and knowledge are usually reliable. But in the context of a fanfic, the author might take this as an opportunity to explore new plotlines and character developments.
He could be seen as an enemy. SHIELD might not take kindly to someone with Harry's potential abilities refusing to join them, and they could view him as a threat. This could lead to them trying to keep an eye on him or even take action against him if they think he's up to no good.
One consequence could be that the story takes a different turn. Instead of the typical heroic plot, there might be a more character - centered exploration. Others around him may have to step up and fill the void. For example, his friends might become the heroes instead.
One consequence could be that he loses out on potential rewards or recognition. Maybe he was expected to win, and his refusal disappoints his supporters. Another consequence might be that it changes the dynamics of the story, as other characters may have to step up or the competition may be less interesting without him.
One consequence is that Harry may lose trust in Dumbledore. In fanfic, this can lead to Harry making decisions on his own, without relying on Dumbledore's guidance. For example, he might go off on his own to search for answers about his parents' death or Voldemort's secrets.
For Harry, he may face a lot of criticism from his friends and the wizarding community. They might see him as a heartbreaker or someone who doesn't value his relationships. This could lead to a strain on his friendships, especially with the Weasley family who he is very close to.
Maybe in the fanfic, Harry has his own ideas and beliefs that conflict with Dumbledore's. He might think Dumbledore's plans are too risky or not in line with his own sense of justice.
Maybe Dumbledore discovers some dark secret about Harry's past that he can't handle. It could also be that Dumbledore is trying to protect Harry in a really strange way, by pushing him away from the dangerous wizarding world around Hogwarts.
One consequence could be a divide in the fan community. Some fans who love fanfiction might feel alienated. They might see this as a lack of acceptance of their creative interpretations.
It could be that Harry finds out about Dumbledore's secrets regarding the Deathly Hallows. If Harry thinks Dumbledore was more interested in the Hallows for his own purposes rather than for the greater good, it might make him hate Dumbledore.
Perhaps Harry has been misled by someone he trusts. They could have filled his head with lies about Dumbledore, making Harry think that Dumbledore is actually a threat. And his motive would then be to protect the wizarding world from what he believes is a hidden danger in Dumbledore.