dumbledore fights

One possible reason could be a misunderstanding. Maybe Harry is led to believe that Dumbledore has been hiding something crucial about his parents' death or Voldemort's return. For example, if Harry discovers some encrypted files in Dumbledore's office that seem to suggest Dumbledore had a prior deal with Voldemort, it could lead to a fight. Another aspect could be related to power. If Harry feels that Dumbledore is being too controlling over his actions and the use of his powers, he might lash out. In the wizarding world, power struggles are not uncommon, and Harry, as a powerful wizard in his own right, might want to assert his independence.

For Harry, his motivation to fight Dumbledore could be pure revenge for Hagrid's death. He might see Dumbledore as a traitor and be consumed by his need for justice. Dumbledore, if he was forced to kill Hagrid, might be motivated by some sort of dark magic compulsion or a threat to something he holds dear, like the safety of the whole wizarding world.

Harry's magic is more instinctive and raw, often fueled by his emotions. So when he fights Dumbledore, his spells would likely be powerful but less refined. For example, he might cast a powerful Patronus in a fit of rage, which could be used as an offensive weapon rather than just for defense against Dementors. Dumbledore, on the other hand, has years of experience and knowledge. His magic would be more precise and strategic. He could use spells like 'Sectumsempra' but with better control, perhaps using it to disarm Harry rather than seriously harm him.

One possible plot twist could be that Dumbledore was under the influence of a dark magic spell that made him kill Hagrid. And Harry, realizing this, has to find a way to break the spell and clear Dumbledore's name while also dealing with his own grief and anger over Hagrid's death.

Snape's loyalty to Dumbledore would be a major driving force. He might see fighting Voldemort as fulfilling Dumbledore's final wishes. Snape would use the guidance and secrets Dumbledore shared with him to strategize against Voldemort. For example, if Dumbledore had some knowledge about Voldemort's horcruxes that he passed on to Snape, Snape could use that information to target them during the fight.

There's also a chance that Dumbledore gets caught by a group of rogue magical creatures. For instance, if he was exploring an area that was supposed to be off - limits to wizards and the creatures there saw him as an intruder. They might not be as rational as wizards and could hold him captive without really understanding who he is.

Well, it could be that Dumbledore has some sort of hidden device or spell that he activates when kidnapped. For example, he could have a charmed object that sends a signal to his allies, like the Order of the Phoenix. His allies then come to his rescue and he manages to escape during the chaos. Also, Dumbledore is extremely intelligent. He might outwit Grindelwald by engaging him in a complex conversation full of riddles and misdirections, which gives him an opportunity to break free.

It could be Severus Snape. He has a complex relationship with Dumbledore. Maybe Snape discovers some of Dumbledore's plans that he doesn't agree with regarding Harry Potter. He then sends a Howler in a fit of anger to express his disapproval.

In a fanfiction, Dumbledore might steal out of desperation. Suppose there was a situation where a curse was about to be unleashed on Hogwarts, and the only way to stop it was by stealing a particular ingredient for an antidote from a place where it was not supposed to be taken. Dumbledore, seeing no other option, decides to steal it. His motive here is to save the school and its students, even if it means breaking the rules.

Fred and George Weasley are very likely candidates. They are known for their love of pranks and their mischievous nature. They might see pranking Dumbledore as the ultimate challenge.