In the fanfiction, they could be forced to work together on a project related to lemons. Maybe there's a local fair that requires everyone to contribute something lemon - themed. Through this shared task, they begin to understand each other better. Harry realizes that Aunt Marge has her own insecurities and Aunt Marge sees that Harry is not the troublemaker she thought he was. For instance, Harry could show his creativity and intelligence during the project, impressing Aunt Marge.
A magical lemon tree could be the catalyst for their relationship development. The lemon tree appears in Aunt Marge's garden and Harry discovers that it has some special magical properties. He tries to protect the tree from being cut down by Aunt Marge. As they interact over the fate of the tree, they gradually build a more complex relationship. Aunt Marge might start to respect Harry's passion for magic and Harry might come to understand Aunt Marge's love for her garden.
Aunt Marge could be developed by showing her having a moment of self - reflection. She might realize that her harsh treatment of Harry was wrong and start to be more empathetic. For example, she could see Harry's kindness towards animals and that could change her view of him.
It could develop into a more tolerable one. Harry might start to see Aunt Marge as a pitiful figure rather than just a mean old woman. Maybe he discovers some things about her past that make him more empathetic.
Maybe she has a secret soft spot for animals, like the dogs she breeds. In a fanfiction, she could find out that some magical creatures are being mistreated, and she decides to use her influence in the Muggle world to help protect them. This would show a different side of her and make her more likable.
One idea could be that Aunt Marge accidentally eats a lemon - flavored magical treat that makes her temporarily nice to Harry. For example, she might start complimenting his schoolwork at Hogwarts instead of her usual mean - spirited remarks.
One interesting storyline could be Aunt Marge learning about the wizarding world and having her views completely changed. Maybe she accidentally stumbles upon Diagon Alley and is amazed by all the magic there. At first she's scared and wants to run away, but then she becomes curious and starts to interact with the magical beings, which in turn changes her perception of Harry and his world.
There could be a 'Aunt Marge likes Harry fanfic'. Fanfic communities are full of diverse interpretations of characters and relationships. It might explore a different side of Aunt Marge's character, perhaps in an alternate universe where she doesn't hold her usual grudges against Harry. You could also try reaching out to Harry Potter fanfic communities on social media platforms to ask if anyone has read or written such a fanfic.
Through shared secrets. For instance, if Harry discovers something about his family that he doesn't want others to know, and he confides in Aunt Lemon. This would create a bond of trust between them.
One possible plot could be that Aunt Marge discovers Harry's difficult situation at the Dursleys and decides to secretly help him with his magic studies. Maybe she has a change of heart after seeing how much he's struggling.
Aunt Lemon might also impact Harry's life by introducing him to a different side of the Muggle world. Maybe she has a love for art or music, and through her, Harry discovers these aspects of Muggle culture that he otherwise would have been deprived of. This newfound interest could help him better understand the differences between Muggles and wizards and appreciate both worlds.
In some fanfictions, Harry could react in a very calculated way. He might start to plot a way to get back at Aunt Marge without using magic in an obvious way. He'd use his wits and the knowledge he has of her weaknesses. For example, if he knows she's very proud of her dogs, he could find a way to make her look foolish in front of others when it comes to her precious pets. All this while still seething about the insults to his parents.