It could be about Sheldon getting back at someone who wronged him in the series. Maybe it's Leonard who ate his last slice of pizza without permission, so Sheldon devises an elaborate plan to make Leonard's life a little chaotic for a while.
Well, perhaps in the fanfiction, Sheldon gets revenge on a bully from his childhood who resurfaces in his present life. He uses his superior intellect to outwit the bully in a very public and embarrassing way, like tricking him into making a fool of himself during a big scientific event.
Perhaps the target is Howard. Howard might have made a joke about Sheldon's mother that Sheldon didn't appreciate. As a result, Sheldon could try to get revenge by interfering with Howard's work on the space station projects, causing minor but annoying setbacks.
The plot could be that Sheldon's friends are highly skeptical at first. They might think it's just a short - lived oddity. However, as the story progresses, they see Sheldon changing in positive ways. His girlfriend could introduce him to new hobbies or social situations that he initially resists but then grows to enjoy.
Well, maybe Boruto's family or friends are hurt by a powerful enemy. So he decides to train hard and seek revenge. He might travel to different places to learn new jutsu and gather allies along the way.
Well, it could be about Issei seeking revenge on those who wronged him in the past. Maybe someone bullied him or betrayed his trust, and now he's out for payback. He might use his unique skills or powers to get even.
Perhaps an intelligent and patient psychologist. She could help Sheldon understand his emotions better. Given Sheldon's complex personality, she would need to be very understanding and be able to handle his idiosyncrasies. This type of girlfriend could also introduce Sheldon to the world of human emotions in a more systematic way.
Maybe Ginny did something that Harry thought was a betrayal, like siding with someone against him in a wizarding conflict. So Harry decides to play some harmless pranks on her to get revenge. For example, he might use magic to make her quill write silly things during a class.
Maybe Harry uses magic to make their house a mess. He could turn Dudley's room into a pigsty or make Aunt Petunia's precious china float and then smash. It's his way of getting back at all the years of mistreatment.
She might get revenge because she felt the Order made a decision that put her or her friends in danger. For example, if they sent Harry on a dangerous mission without proper support, Hermione could plan some elaborate scheme to teach them a lesson. Maybe she'd use her intelligence to expose some of their secrets or weaknesses.
Well, it could be that Rumple discovers some past wrong Dumbledore did to him or his kind. Maybe Dumbledore once meddled in Rumple's magical affairs and now Rumple wants to make him pay. He could start by using his unique magic to create chaos in Hogwarts, like making the staircases go haywire or the portraits misbehave.
Maybe Ron accidentally ruins Hermione's important experiment in the wizarding lab. In the fanfiction, Hermione could get revenge by getting all their mutual friends to side with her in an argument. She could present all the facts about how Ron's carelessness has cost her time and effort, making Ron feel isolated and guilty.