It could be an older wizard who has retired from the Ministry of Magic but is drawn back into action as a cursebreaker. He has years of experience dealing with all kinds of magic, both good and bad. He might be a bit of a loner, having seen too much of the darker side of the wizarding world. His main motivation could be to make amends for some mistakes he made in his past while working for the Ministry, and he sees curse - breaking as a way to do that.
A Muggle - born witch who has always felt like an outsider in the wizarding world could be the main character. She discovers curse - breaking as a way to prove herself and show that Muggle - borns are just as capable as pure - bloods. She uses her unique perspective, having grown up in the Muggle world, to approach curse - breaking in different ways. For example, she might use some Muggle concepts or tools in combination with her magic to break curses that others have found impossible to deal with.
Obviously, Harry Potter is a main character as it's in the title. He's the one taking on the role of the cursebreaker. Hermione Granger could also be a main character as she is often by Harry's side in the original series and her knowledge would be very useful in cursebreaking.
For Harry Potter cursebreaker fanfiction, an interesting character could be Finn. Finn is a self - taught cursebreaker who grew up in the wizarding slums. He has a rough exterior but a heart of gold and a natural talent for breaking curses. He often uses unorthodox methods that other cursebreakers might scoff at. Another character is Seraphina. She is a cursebreaker who is also a seer. Her visions sometimes help her in her cursebreaking work, but they can also be a hindrance as they are often unclear. And a third character is Eamon. Eamon is a cursebreaker from a long line of cursebreakers in Ireland. He has a deep knowledge of Celtic magic and uses it to break curses that are related to ancient Irish curses.
One idea could be that the cursebreaker discovers an ancient and forgotten curse in the Forbidden Forest that is slowly spreading and affecting the magical creatures there. They have to team up with Hagrid to find a way to break it before it reaches Hogwarts. Another could be a cursebreaker who is on a quest to find the origin of a powerful dark curse that was used in the past by Voldemort's followers and is now resurfacing in a different form. The cursebreaker travels to different wizarding locations around the world to gather clues.
It could be a group of dark wizards who don't want Harry to succeed in becoming a cursebreaker. They might be using dark curses themselves to cause chaos in the wizarding world, and they see Harry as a threat to their plans. So they try to stop him at every turn, whether it's by setting traps or sending out cursed creatures after him.
A lesser - known character like Ernie Macmillan from Hufflepuff could be the main character. As a prefect, he could bring out the unique qualities of Hufflepuff house. He might have to deal with issues like other houses underestimating Hufflepuff students. His story could focus on how he promotes the values of hard work, loyalty, and fairness within the house and the school as a whole.
Hermione could be a great main character. She's curious and intelligent, so she would be really interested in exploring the secrets of the diary. She could use her vast knowledge of magic to try and figure out how the diary works and what secrets it holds.
Harry Potter himself could be the main character as a revenant. Maybe he has some unresolved issues from his past, like his relationship with his parents. His revenant form could be on a journey to fully understand their sacrifice and his own place in the wizarding world's history.
It could be a younger sibling of one of the main characters in the original series. For example, Ginny's little sister who has big shoes to fill but also a great passion for Quidditch.
Hermione could be a great main character in an elementalist fanfiction. Her intelligence and thirst for knowledge would make her eager to learn about and master elemental magic. She could be the one to discover a long - lost elemental spell book and start exploring the powers.
It could be a new student at Hogwarts who has a natural talent for dealing with beasts. This student could be from a family that has always had an affinity for magical creatures but has kept it a secret until now.