McGonagall could also be a supporting character. She could pop in to check on Harry and Dumbledore. Maybe she brings some freshly baked magical treats for them to enjoy while Dumbledore tells Harry stories about Hogwarts' past. She could also add some of her no - nonsense wisdom to their interactions.
Hagrid could be a great supporting character. He could bring some interesting magical creatures for Dumbledore and Harry to interact with. For example, he might bring a baby dragon that Dumbledore could use to teach Harry about the care and danger of such powerful creatures.
Luna Lovegood could be a supporting character. She has an open - minded and unique perspective. She might support Harry in his defiance, understanding his reasons when others don't. Maybe she helps him see things from a different angle or provides some crucial information that validates his decision to defy Dumbledore.
One possible plot could be Dumbledore taking Harry on a magical tour of Hogwarts. He shows Harry secret passages and tells him stories about the founders. For example, they could visit the Room of Requirement together and Dumbledore could explain how it works. This would not only be an educational experience for Harry but also a chance for Dumbledore to bond with him on a more personal level.
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.
Well, obviously Harry Potter. He's the main protagonist in the original series and in the bashing fanfictions, he might be the one to finally see through Dumbledore's facade. Ron Weasley could also be popular. He's Harry's best friend, and in these stories, he might support Harry in his doubts about Dumbledore. And then there's Voldemort. Some fanfictions might use Voldemort as a tool to show how Dumbledore's actions or inactions affected the battle against him. For example, if Dumbledore was so secretive, it could have made it easier for Voldemort to gain power.
Neville is also quite popular. His growth from a somewhat clumsy and timid student to a brave and confident member of Dumbledore's Army is a great source of inspiration. In fanfics, he might be given even more heroic moments, like leading the group in a crucial battle or discovery.
There could be a mechanic named Tom. He helps Harry keep his helicopter in top shape. Whenever Harry has a problem with the helicopter, Tom is there to fix it.
Hermione could be a likely helper. She's smart and resourceful, and she would likely believe Harry if he told her his reasons for escaping Dumbledore. She could use her vast knowledge of magic and spells to create distractions or to find ways to bypass Dumbledore's security measures.
Well, Harry might outsmart Dumbledore by using his unique understanding of the magical world in ways Dumbledore doesn't expect. For example, Harry has a more direct experience with some dark magic items due to his encounters with Voldemort. He could use this knowledge to make decisions that seem counter - intuitive to Dumbledore but are actually more effective in a particular situation.
One possible reason could be that Harry breaks school rules in the fanfiction. For example, if he ventures into the Forbidden Forest without permission. Dumbledore is strict about the safety of students and such disobedience might lead to punishment.
The Weasley family as a whole might also support Harry. They have always treated Harry like one of their own. Arthur Weasley, being an open - minded wizard, might understand Harry's perspective. Ginny, who is very close to Harry, would surely be on his side as well. They would see Harry as more than just a student defying a headmaster, but as someone fighting for what he believes is right.