I'm not sure specifically as there could be many different versions of such fanfiction. It might be about a character named Bella who decides to fight back against some sort of antagonist, perhaps in a fantasy or science - fiction setting.
In a dark corner of Hogwarts, Harry was fuming. Malfoy had once again taunted him about his parents. Harry's eyes blazed with anger. Without a second thought, he lunged at Malfoy, his wand at the ready. 'You won't get away with this anymore, Malfoy!' he shouted. Magic crackled in the air as they dueled, Harry's newfound determination pushing him forward.
Thomas the Tank Engine was created by the Reverend W. Awdry. He was based on the steam engines that Awdry saw on the railways. Thomas was a cheeky little blue engine. He worked on the Island of Sodor, which is a fictional place filled with many other engines, tracks, and stations. His adventures usually involve learning lessons about being a good engine, like being helpful, not being too boastful, and working well with the other engines on the railway.
Since I haven't read it, I can't say for sure. But presumably, Bella is one of the main characters. There could also be other characters like her friends, family, or the antagonists she is fighting against.
Well, it could be that Harry is facing some new dark forces in the fanfiction. Maybe he discovers a hidden group of dark wizards who are plotting against Hogwarts, and he decides to fight back to protect his school and friends.
It could be a new group of rogue ninjas who have a vendetta against Konoha. They might be led by a powerful and cunning ninja who has a personal grudge against Naruto or the village in general.
Perhaps in this 'harry fights back fanfic', Harry discovers some new powers or spells that he uses to fight back. He could be tired of being pushed around by Voldemort's followers or other bullies in the magical community, and he uses these newfound abilities to protect himself and his friends. For example, he might learn an ancient spell from a hidden book in the restricted section of the library. This spell gives him an edge in combat and he starts to turn the tables on his adversaries.
His friends like Ron and Hermione would surely be his allies. They have always been by his side in the original stories, so it's likely they'll be there in the fanfiction too, helping Harry in his fight.