Hermione might be the one. With her extensive research skills and vast knowledge of magic, she could have stumbled upon a way to remove the scar. She was always determined to help Harry, and this would be just another of her great contributions.
In the fanfiction, perhaps Harry would finally be free from the constant reminder of his encounter with Voldemort. His life might become more normal, without the stares and whispers related to the scar. He could focus more on his own growth and development as a wizard, rather than being defined by his past trauma.
One interpretation could be that the scar is a physical manifestation of the threat of death that has always loomed over Harry. Voldemort's attempt to kill him as a baby left a mark that is constantly a reminder of that near - death experience. It could also symbolize that Harry has a connection to death in a more mystical way, like being able to sense when death is near or having a certain immunity to some of the more terrifying aspects of death magic because of his own encounter with it at such a young age.
In some fanfictions, Naruto might get the scar on his eye during a particularly intense battle with a powerful enemy. Maybe it was a close encounter with a rogue ninja's weapon that managed to leave a mark on his eye area.
Todoroki got his scar because of his father's cruel actions. His father, Endeavor, deliberately caused the scar to try and shape his son's powers.
One interesting scenario could be that the removal process involves a unique magical spell that only Harry, with his special connection to Voldemort, can perform. This spell might require him to draw on his deepest reserves of courage and love for his friends.
It can introduce a darker and more mysterious element to the plot. For example, if Harry discovers that he has death in his scar, he might become more withdrawn as he tries to understand what it means. This could lead to him isolating himself from his friends, which in turn affects the group dynamics.
In some fanfics, Percy's scar on his face could be a result of a betrayal. Perhaps a so - called ally turned on him during a mission. This person, who Percy trusted, secretly attacked him, leaving a scar on his face. This would add a layer of emotional depth to Percy's character, as he would have to deal with the pain of betrayal along with the physical reminder of it on his face.
His scar might make some people more intimidated by him. They could see it as a sign of his dangerous experiences and be a bit afraid to get too close. For example, new acquaintances in the fanfic might be hesitant to approach him at first.
Dumbledore could also play a role, even if it's from beyond the grave. Maybe he left behind some clues or instructions that Harry only discovers when he's in the middle of trying to remove the Horcrux.
The portraits could offer him emotional support. Just seeing his parents' faces might give Harry the strength to face difficulties. For example, when he's feeling down or facing a tough decision, looking at the portraits could be like getting a warm hug from his parents, even if they're not physically there.