Dumbledore, if he were still alive, would be very cautious. He would try to guide Harry towards using his powers for good, or at least in a way that doesn't disrupt the balance of the wizarding world. The other Hogwarts professors would likely be split. Some would be horrified and want to expel Harry, while others would see it as an opportunity to study a rare form of magic and its implications.
The teachers at Hogwarts, like Dumbledore (if he were still alive in the fanfic), would be deeply concerned. Dumbledore always saw great potential in Harry for good. He would probably try to understand what led Harry to this path and would use all his wisdom and magic to try and turn Harry back. The other teachers would also be on high alert, fearing for the safety of the students and the future of the wizarding world.
Hermione would be devastated. She has always been Harry's loyal friend and believed in the fight against the Dark Lord. She would probably try to convince Harry to come back to the right side, reasoning with him about the evil nature of the Dark Lord's actions. Ron, on the other hand, would be both angry and confused. He might initially think it's some sort of joke or that Harry has been tricked.
Ron would be devastated. He's been their best friend for years. He'd probably try to talk them out of it at first. If that fails, he might have to choose between loyalty to his friends and what he believes is right. The Hogwarts professors, like Dumbledore (if he were still alive in the fanfiction), would be very concerned. Dumbledore would likely see it as a great loss of two of the brightest lights in the wizarding world. He might try to find a way to reverse whatever led them down this dark path.
He could be shocked. Maybe there are some fanfictions that take a very dark turn or have unexpected pairings that he never thought of. He'd probably need some time to process such strange ideas. And he might also be curious to see how far the creativity of the fans can go. He might even get some new ideas about his own life from reading some of the more imaginative fanfictions.
Harry Potter would likely be on high alert immediately. He has experience with fighting Dark Lords, so he would start gathering his old friends and allies. Hermione would be researching like mad, trying to find any weaknesses of this new Dark Lord. Ron would be a bit more hesitant at first but would soon join the fight. The younger generation, like Ginny and Neville's students, would be both scared and determined to prove themselves in the face of this new threat.
He may be confused at first. Fanfics can be very different from his real experiences. He might wonder why people write such things about him and his world.
The characters included the supporting role-Nicolas Flamel, the male lead-Wright, the child before Hogwarts, the female lead-Chang Chu, the male lead-Harry, the male lead-Dumbledore, the female lead-Hermione, and the female lead-Verita.
"Harry Potter: Dark Alchemy" by Wei Tubai. It's a light novel/derivative doujinshi novel with transmigration and system elements. It's finished and can be enjoyed without worry.
[User recommendation: The writing style and the setting of the female protagonist are so exciting. The female is strong and the male is weak. The protagonist is too pure.]
I hope you will like this book.
Most of the wizarding world would probably be horrified. The Dark Mark is a symbol of Voldemort and his Death Eaters, so people would be very suspicious of Harry. They might think he has turned to the dark side.
Harry might initially be shocked and confused. He's used to Hogwarts being his safe haven, so when it turns against him, he'll be at a loss. He may try to prove his innocence by finding evidence or confronting those who are spreading lies.