Who could be the main antagonist in 'harry makes a different choice fanfiction' if Harry makes a different choice?

Well, it could be that Harry makes a different choice regarding his friends. Instead of befriending Ron and Hermione, he might choose to hang out with some of the other students who are often overlooked, such as Neville. This would change the dynamics of the group and how they face the various threats at Hogwarts. It could also lead to Neville developing more confidence earlier in the story because of Harry's influence.

The unique plot twists and well-developed characters make it stand out. It takes familiar tropes and gives them a fresh spin.

Perhaps it would be a new character entirely. A powerful wizard who is jealous of Harry's arrival in this new world and sees him as a threat to his own power and status. This wizard could have control over a group of magical beings that are unique to this world and use them to oppose Harry at every turn.

It could be a new dark wizard that is specifically drawn to Harry because of his different Patronus. This wizard might see Harry's unique Patronus as a threat to his own plans for power or chaos in the magical world.

It could be Dumbledore. In this fanfiction, Dumbledore might see Harry making a Horcrux as a threat to the wizarding world and tries to stop him at all costs. He could be the main antagonist because he stands in the way of Harry's actions, even if Harry has what he believes are good reasons for making the Horcrux.

It could be a dark wizard who wants to capture Pikachu for its powerful electric abilities. He might plan to use Pikachu's electricity to power some sort of dark magic device.

It could be a dark wizard who has a vendetta against the Weasley family. Since the twins are part of the Weasleys, this dark wizard targets them. Maybe he blames the Weasleys for something that happened in the past, and the twins, being the more adventurous and visible members of the family, become the main targets.

Since it's a fanfiction based on Harry Potter, Harry Potter himself would likely be one of the main characters. But depending on the nature of the wrong choice, other characters like Hermione, Ron, Dumbledore or even some of the villains like Voldemort or Malfoy could also play significant roles.

One aspect that makes different Harry fanfiction appealing is the creativity of the authors. They can take the basic elements of the Harry Potter world, such as the magic, the Hogwarts school, and the characters, and remix them in countless ways. Some fanfictions might focus on a different time period in Harry's life, or they could introduce new magical creatures or spells. This variety means there's always something new to discover for fans of the series. Also, different fanfictions can explore different emotional arcs for Harry, like a more angsty or a more comical take on his journey, which broadens the overall experience of the story.

It could be Dumbledore. He is known for his strategic thinking and protecting Harry. Maybe he believes that a different name will keep Harry safer from Voldemort or other threats. Dumbledore has a deep understanding of the magical world and might have some secret knowledge about the power of names.