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.
Obviously, King himself is a very popular character in 'One Punch Man King' fanfiction. He is often the center of the story, whether it's about exploring his mysterious powers or his relationships with other heroes. Another popular character is Saitama. Since they are both part of the hero association, there are many fanfictions that involve their interactions, like Saitama being curious about King's supposed feats of strength.
One interesting 'One Punch Man King' fanfiction could be where King actually has some hidden powers that he's been suppressing. In this fanfic, he might start to slowly reveal his true strength during a really tough battle against a new and extremely powerful monster. It could be a story that focuses on his internal struggle between wanting to keep his low - key image and having to step up to protect the city.
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.
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.