The wizarding world would likely be plunged into a state of despair. Harry was seen as the 'Chosen One' to defeat Voldemort, so without him, there would be a sense of hopelessness. Voldemort would probably have free rein to impose his dark rule without much opposition at first.
There would be a significant shift in the power balance. With Harry gone, the Order of the Phoenix would be severely demoralized. However, this could also lead to new heroes emerging from unexpected places. Some characters who were in Harry's shadow might step up to try and resist Voldemort in different ways. For example, Neville Longbottom could potentially become a more central figure in the fight against Voldemort, gathering other students and witches and wizards who were still willing to resist.
The magical creatures might also be affected. Harry had a certain connection with some of them, like the centaurs. Without Harry, they might become more withdrawn or even side with Voldemort if they feel that the wizarding world has no real chance of fighting back. Hogwarts itself would become a very different place. It could turn into a more authoritarian institution under Voldemort's influence, with Dark Arts being taught more openly and students being forced to follow strict and cruel rules.
The Death Eaters would initially be overjoyed. They would think that with Harry on their side, they are invincible. But some of them might also be suspicious of Harry's motives, fearing that he is a double - agent. As for the general wizarding population, they would be terrified. Harry was seen as their hope, and now that he has joined Voldemort, they would feel completely hopeless and defenseless.
The wizarding world would be in chaos. The Order of the Phoenix would be extremely worried and likely try to rescue Harry. The Death Eaters, on the other hand, might see it as a sign of Voldemort's power and dominance. Hogwarts would also be affected, with teachers and students fearing for the future of the wizarding world.
If Voldemort won the war in fanfiction, the wizarding world would experience a total transformation. First, the Ministry of Magic would be under his complete control. His Death Eaters would be in charge of all the important positions. The concept of justice would be warped, and any form of opposition would be brutally suppressed. The wizarding economy would likely suffer too as Voldemort's focus would be on power and domination rather than development. Also, the relationships between different magical creatures would be disrupted as Voldemort has no respect for any form of life other than his own pure - blood ideology.
Well, the pure - blood families who were on the fence about Harry might finally accept him wholeheartedly. They would see that he was the one who could truly rid the wizarding world of Voldemort. However, there would also be those who would be critical. Some of the more traditional wizards and witches might think that using a shooting method was too violent and un - wizard - like. They might worry that this sets a bad precedent for future conflicts in the wizarding world. But overall, the general public would be relieved that Voldemort was finally gone and would likely celebrate Harry as a savior.
The Ministry of Magic would be in a difficult position. On one hand, they would need to keep the wizarding world calm. On the other hand, they would have to deal with the fact that a muggle family killed a famous wizard. There would be debates about how to handle the Dursleys. Some might want to obliviate their memories and send them to Azkaban, while others might think that a more public trial is necessary to show that the wizarding world does not tolerate such actions against one of their own.
The wizarding world would be in chaos. Harry, being Voldemort's right - hand man, would be a huge threat. He knows many of the Order of the Phoenix's secrets. Hogwarts would no longer be a safe haven. The students would be in constant fear as Harry could use his inside knowledge to help Voldemort attack the school. The Ministry of Magic would also be in a difficult position as they had once relied on Harry to be their savior.
The wizarding world would become more open to Muggle - borns. Harry being a Muggle - born advocate would ensure that there are no discriminatory practices against them. He might also make Hogwarts more accessible to students from all backgrounds, not just those with a magical family history.
In fanfiction, Harry Potter can change the Wizarding World in many ways. For example, he might introduce new spells or magical concepts that were not in the original series. He could also have different relationships with other characters, which in turn would affect the social dynamics of the Wizarding World.
The wizarding world would likely be in an uproar. Many would see it as a betrayal of all that Harry stands for. After all, he's the hero who defeated Voldemort. Others might be intrigued by the idea, seeing it as a way to explore the complex relationship between the two. Some might worry that it gives Voldemort too much credit or glorifies him in some way.
There would be a great deal of shock and confusion. Many would start to question everything they had believed in. Families would be divided. Some might think that Harry had been corrupted by Voldemort's dark magic and try to find a way to reverse it. The Ministry of Magic would be in a panic. They would try to come up with new strategies to deal with this new threat. Teachers at Hogwarts would be worried about the safety of their students. And the Death Eaters, while initially happy to have Harry on their side, would also be suspicious of his motives and loyalty.