Often, Dumbledore as Death would be a very complex character. He may not be the straightforward evil or good. His role might be more about maintaining a balance in the wizarding world, which is similar to the concept of Death in some mythologies. He could be using his influence on the different characters in different ways. For instance, his relationship with Snape could be a part of his plan as Death. Snape's actions, which were so crucial in the original story, might be reimagined as being directly or indirectly guided by Dumbledore - as - Death. This could add a whole new layer of mystery and intrigue to the fanfiction.
One key plot point could be Dumbledore's true identity being revealed gradually. Maybe Harry starts noticing strange things about Dumbledore that make him suspect he is not just an ordinary wizard but Death itself. Another could be how the prophecy about Harry and Voldemort fits into this new paradigm where Dumbledore is Death. It might change the meaning of the prophecy completely, as Dumbledore - as - Death could have a different intention behind the events related to the prophecy.
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.
He might give Harry detention. Harry could be made to clean the trophies in the trophy room or help Hagrid with some difficult tasks in the Forbidden Forest under strict supervision.
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.
Well, in certain Harry Potter fanfiction, Dumbledore can come across as insane. It really depends on the writer's interpretation and the direction they want to take the story. Some might do it for shock value, to create a more edgy or different take on the well - known character. However, the canonical Dumbledore was a highly intelligent and calculating figure, not insane.
It's a really horrible idea. In the original 'Harry Potter' series, Dumbledore is like a father figure to Harry. Their relationship is based on trust, guidance and mutual respect. This idea completely subverts the positive image and relationship established in the original work.
I haven't come across such a disturbing fanfiction myself. In the official 'Harry Potter' lore, Harry and Dumbledore have a mentor - mentee relationship and there's no such violent scenario. Fanfiction that goes against the core values of the original work like this is not only untrue to the spirit but also quite abnormal.
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.
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.