Some of the students who have been through tough times at Hogwarts due to Voldemort's influence might also side with Harry. Neville, for example, has shown great courage and has his own ideas about how to deal with the dark forces. He might see Harry's defiance as a necessary step in the fight against the common enemy, and join him in his stand against Dumbledore if he believes it is for the greater good.
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.
In such a fanfiction, one possibility could be that Harry Potter defies Dumbledore over the use of certain dark magic items. Maybe Harry believes that Dumbledore is being too cautious and that these items could be used for good in the fight against Voldemort. For example, he might think that the Elder Wand could be harnessed in a different way than Dumbledore anticipates.
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 that Harry discovers some dark secret about Dumbledore's past actions and decides to oppose him. For example, if he finds out that Dumbledore had some sort of deal with the Dark Arts that he hid from everyone. This would make Harry feel betrayed and drive him to defy Dumbledore.
For Harry, his friends like Ron and Hermione are likely to be his allies. They've always been by his side through thick and thin in the original series, so it's natural for them to support Harry in a confrontation with Dumbledore. Neville could also be an ally, given his growth and courage shown in the books.
Hermione would be a likely candidate. She is Harry's best friend and is very intelligent. She could use her knowledge of spells and magic to come up with a plan to help Harry escape. For instance, she might create a diversion or find a way to disable the security around Dumbledore's area.
The main characters would be Harry and Dumbledore. However, the antagonists could also be important. If there is a new dark force in the fanfiction, they would be the ones Harry and Dumbledore are up against. Voldemort's remaining followers could also be part of the equation. Their actions could be what drives Harry to submit to Dumbledore's leadership, as they pose a significant threat to the wizarding world and Harry realizes he needs Dumbledore's guidance to face them.
Hermione could be a main character. She might use her vast knowledge to help Harry and Dumbledore in their adventures. For example, she could research ancient spells or potions that are crucial for their mission.
Hermione would be a likely supporter. She is always loyal to Harry and if he presented her with evidence of Dumbledore's wrongdoings, she would probably side with him. She has the intelligence to help Harry strategize and find ways to expose Dumbledore. For example, she could use her research skills to dig deeper into Dumbledore's past.
Some of the younger students who looked up to Harry, like Neville, could support him. Neville has grown to be a strong and brave character. He might see Harry's actions as a way to make the wizarding world a better place. Also, those students who have felt wronged by Dumbledore's decisions in the past, perhaps in terms of school policies or safety, could come forward to support Harry in the court case.
Hermione might support Harry if she also sees some flaws in Dumbledore's leadership. She is very logical and if Harry presents her with solid evidence, she could side with him. For instance, if Dumbledore's actions are putting students in danger in some way, Hermione would want to protect her fellow students.