A lot of fanfictions play with the idea of Boros having some hidden power or strategy that makes the fight more intense and less one - sided than in the original. For example, he might have a power - up that actually challenges Saitama for a while. Another plot could be a time - travel twist where someone goes back in time to change the outcome of the Saitama vs Boros fight, which then has all kinds of consequences for the One Punch Man universe.
Well, some dedicated anime fan communities might also be a good place to look for such fanfiction. For example, Reddit has sub - reddits related to One Punch Man where fans might share or recommend their favorite 'Saitama vs Boros' fanfictions. Also, Tumblr often has fan - created content including fanfiction, so it's worth a search there too.
Toge Inumaki is important too. His special cursed speech ability makes him stand out. Also, the principal of the school, Masamichi Yaga, is likely to be important as he is in a position of authority and has an influence on Gojo and the other students. There could be other characters like the members of different clans that also play roles in the complex web of the story.
Good female Boros fanfiction often has a well - developed character. It should capture her strength and power. For example, it might show her in intense battles. Also, it should have a good plot. Maybe it could involve her making tough decisions that affect her world.