It's hard to say without reading it. It could be the original characters like Harry, Hermione, and Ron if it's a continuation of their story. Or it might focus on new characters created by the fanfic author.
There could be the children of the original characters. For example, Harry Potter's son or Hermione Granger's daughter might be main characters.
Harry Potter himself is likely to still be a main character. He's the face of the series. Hermione and Ron will probably also be important. But new characters might be introduced too, perhaps a mysterious new student or a powerful wizard from a far - off land.
Most likely Harry Potter himself. But there could also be other familiar characters like Hermione, Ron, and Dumbledore.
A former Death Eater who has had a change of heart could be the main character. They are now trying to make amends and start a new life. Their past experiences would make them a complex and interesting character as they struggle to fit into the new, post - Voldemort wizarding society.
There could be a group of rogue Death Eaters who escaped justice and have banded together again. They believe that Voldemort's ideas were right but that he was too weak. So they target Harry, thinking that if they can defeat him, they can finally achieve their goal of a pure - blood - dominated wizarding world. They might be more cunning and less flashy than Voldemort, making them a more difficult enemy to detect.
It could be about Harry's life after the events of the original series, maybe with new magical adventures or challenges.
Obviously, Harry Potter himself would be the main character as the story is centered around his new look. His friends like Ron and Hermione would also be important characters as they would react to his new look and help him deal with any consequences. And there could be new characters introduced, perhaps a mysterious wizard who is somehow related to the cause of Harry's new look.
Since it's a Harry Potter fanfic with 'a new beginning' in the title, it could center around a major shift in the existing relationships in the series. It could be that Harry, Hermione, and Ron start a new chapter in their lives where they have to deal with long - forgotten secrets that surface. This fanfic might also introduce new magical creatures or spells, and show how these elements change the dynamics of the wizarding world they know.
There could be a new wizard student from a far - off land. This student might bring with them unique magical traditions and powers that Harry and his friends have never seen before.
There could be a new professor at Hogwarts. Maybe a young and brilliant wizard who has just returned from a long journey in a far - away magical land. This professor could bring in new ideas and spells, and become an important figure in Harry's new path.