One interesting crossover could be Saitama from One Punch Man meeting Ichigo from Bleach. Imagine Saitama's nonchalant attitude in the face of Bleach's complex spiritual world. He might just punch away Hollows without breaking a sweat, while Ichigo would be both amazed and a bit frustrated at Saitama's overpowered nature.
The appeal lies in the combination of two very different universes. One Punch Man has a modern, comical take on superheroes with Saitama's extreme power, while Bleach is a more complex world of souls, Shinigami, and Hollows. When combined in fanfiction, it creates unique scenarios. For example, seeing how Saitama would react to the strict hierarchy of the Soul Society or how Ichigo would deal with the rather simple - minded villains in One Punch Man.
One interesting crossover could be Saitama from One Punch Man meeting Ichigo from Bleach. Saitama's overpowering strength would contrast with Ichigo's growth - based power. Maybe Saitama could accidentally disrupt a Hollow attack that Ichigo was about to face, leading to some comical misunderstandings as Ichigo tries to figure out who this bald - headed, super - strong guy is.
Genos and Rukia could also be a popular pairing. Genos' robotic nature and his loyalty to Saitama could be an interesting contrast to Rukia's cool and collected Soul Reaper self. They might have some unique interactions, like Genos being curious about Rukia's zanpakuto and spiritual powers.
Another storyline could be that Thanos, aware of One Punch Man's power, tries to use the Infinity Stones to either eliminate him or make him an ally. There could be a long - drawn - out battle where One Punch Man has to constantly dodge Thanos' attacks while trying to find a way to land his one punch. In the end, he manages to do it and saves the day.
One interesting storyline could be that Goku, being the ever - eager fighter, challenges Saitama not knowing the true extent of his power. Saitama, on the other hand, is just looking for a normal grocery shopping day. The clash of their personalities, Goku's excitement and Saitama's nonchalance, could lead to a very comical start. Then as the fight progresses, they both start to respect each other's power in different ways.
In a one - on - one fight between One Punch Man (Saitama) and Goku, it's really tough to say. Saitama is known for being able to defeat any opponent with just one punch. However, Goku has a vast array of powerful forms and techniques. If Saitama landed his first punch, he'd win instantly. But Goku's speed and ability to constantly power up could potentially give him an edge. He could keep dodging Saitama's punches until he found a way to overpower him. It really depends on how the fight is set up in the fanfiction.
One interesting scenario could be that Saitama and Tornado team up against a super powerful villain that neither could defeat alone. Their different powers - Saitama's overwhelming strength and Tornado's psychic abilities - would make for an exciting combination.
One possible plot could be that Tornado initially challenges Saitama out of pride. She sees his nonchalant attitude and wants to prove that her psychic powers are superior. Saitama, being Saitama, just goes along with it. As the battle unfolds, Tornado throws everything she has at Saitama, but he just dodges casually. Eventually, Saitama throws a light punch that knocks Tornado back, but not seriously hurt, which makes her realize his true strength.
Saitama's power is his physical strength which is seemingly limitless. Tornado, on the other hand, has psychic powers. If Tornado could somehow manage to immobilize Saitama before he throws a punch, she might have a chance. However, Saitama has shown resistance to various attacks. In most fanfictions though, the outcome often depends on the theme the writer wants to convey. If it's about the power of the underdog, Tornado might win. But if it's about the ultimate power, Saitama is likely to come out on top.