Saitama is a very powerful hero in the One Punch Man universe. He can defeat any opponent with just one punch. He has a simple appearance and a somewhat laid - back personality.
Sometimes King is paired with Saitama. King, known for his false reputation of being a super - strong gamer in the original story, could be in interesting interactions with Saitama in the fanfiction's gaming context. Maybe they compete in a gaming tournament within the fanfiction, and Saitama's effortless wins baffle King.
Sure, She-Hulk is related to Hulk. Jennifer Walters, aka She-Hulk, got her powers because of a blood transfusion from her cousin Bruce Banner, who is Hulk. This connection is a key part of their storylines in the comics.
Captain America would be a great addition. His leadership and moral compass could guide Hulk and She - Hulk when they face difficult decisions. And his combat skills could come in handy during battles.
Genos could be an unexpected opponent. He might be forced to fight Saitama due to some mind - control or a misunderstanding in the rules of the tournament. It would be really interesting to see how Saitama would handle fighting his own disciple, and how Genos would fare against his master's incredible strength.
Comics usually depict Hulk as stronger than She-Hulk. Hulk's strength levels are often at a much higher magnitude, but it doesn't mean She-Hulk is weak by any means. She has her moments and skills that contribute to her being a significant character in the comic universe.