In a battle between One Punch Man and Superman, it's really tough to say. One Punch Man can defeat any opponent with just one punch. But Superman has incredible strength, speed, and a whole bunch of other powers like heat vision and flight. If One Punch Man managed to land his one punch, he could win. However, Superman's speed might make it difficult for One Punch Man to even get a hit in. So, it could go either way depending on the circumstances.
Similarities? Well, both are super - powerful. They both are often the ones to save the day in their respective universes. Differences? One Punch Man's power is very straightforward - that one punch. Superman has a whole range of powers. In fanfiction, One Punch Man might be more of a comical character in his overpoweredness, while Superman is more of a traditional hero figure.
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.
In a fanfiction scenario between Tornado and Saitama, Saitama would likely win. He's so overpowered that he can defeat any opponent with one punch. Tornado is extremely strong with her psychic powers, but Saitama's strength seems limitless. His simple training routine has made him so powerful that no enemy has been able to withstand his punch so far.
Yes, there likely is. The Naruto and One Punch Man fandoms are both quite large, and it's common for fans to create crossover fanfictions. These crossovers can be really interesting as they combine the unique elements of both universes, like Naruto's ninja skills with Saitama's one - punch power.
I'm quite sure there exists a 'Naruto is One Punch Man' fanfic. The world of fanfiction is vast and full of all kinds of creative crossovers. Writers might be intrigued by the idea of bringing Naruto's ninja skills and the unique world of One Punch Man together. For example, how would Naruto react to the overpowered villains in One Punch Man's world? And how would Saitama view Naruto's determination to protect his village? These are the kind of things that could be explored in such a fanfic.