What are some possible reasons in fanfiction for Sirius Black to disown Harry Potter?

One possible reason could be a misunderstanding. Maybe some false information was spread about Harry that made Sirius believe he had done something unforgivable. For example, if there were rumors that Harry was involved with dark magic in some way, Sirius, who has a strong aversion to the dark side, might be quick to disown him.

A common reason could be misinformation. In the wizarding world, rumors can spread quickly. If a false rumor about Harry being involved in dark magic activities got to Sirius, he might disown him. For example, if someone planted evidence that Harry was secretly communicating with Death Eaters.

One possible reason could be miscommunication. Maybe Harry does something that Sirius misinterprets as a betrayal or a stupid mistake, leading to Sirius lashing out.

One possible reason could be a misunderstanding. Maybe he discovers some secrets about his parents that he misinterprets. For example, if he finds out they were involved in some dangerous or morally ambiguous activities in their youth that he doesn't fully understand at first.

Maybe Sirius wants to train Harry himself. In fanfiction, he could believe that he has a better understanding of the Dark Arts and how to fight Voldemort compared to the professors at Hogwarts. So, he kidnaps Harry to start his own special training regime away from the school.

Perhaps a plotline where Sirius Black discovers a hidden prophecy related to Harry Potter that requires Harry to submit to Sirius in a series of magical trials. These trials could be designed to unlock Harry's true potential. Or it could be a plotline where the wizarding world is in chaos, and Sirius, with his knowledge and experience, convinces Harry that submitting to his leadership is the only way to restore order. This could involve Harry following Sirius' orders in battles, in diplomatic relations with other magical creatures, and in reforming the Ministry of Magic.

Well, one possible reason could be a dark magic spell that forces Harry to do such a thing against his will. Maybe a powerful dark wizard has put a compulsion charm on him. Another reason could be a misinterpretation of a prophecy that makes someone believe Harry must perform this act to prevent a greater evil. However, this is a very strange and dark concept for a fanfiction.

One reason could be the strong bond between them in the original story. Fans might have felt that it could be developed into a father - son relationship in fanfic.

One reason could be Harry's impulsiveness. Harry often jumps into dangerous situations without thinking, and Sirius, being his godfather and having a protective nature, would shout at him to make him realize the risks. For instance, if Harry decides to go after a Death Eater alone.

Well, if Sirius Black hates Harry Potter fanfiction, it could lead to a divide among fans. Some fans might respect his view and be more critical of fanfiction themselves, while others might disregard his feelings. Also, it could potentially limit the creativity within the fan community as people might be afraid to create content that could be seen as disrespectful to Sirius Black's character.