One of the things that make 'sonic x saitama fanfic' so appealing is the potential for character development. Sonic, who is used to being the hero in his own world, has to adjust to Saitama's way of doing things. And Saitama, who is often bored with the lack of challenge in his world, finds Sonic's energy and his world's constant threats exciting. This interaction between the two characters allows for new relationships to form, new challenges to be faced, and new adventures to be had, which is what makes these fanfics so engaging for readers.
Sure. One popular 'sonic x saitama fanfic' might be 'The Unexpected Team - Sonic and Saitama'. It's about Sonic's super - speed adventures colliding with Saitama's one - punch power. Another could be 'Sonic's Speed Meets Saitama's Strength' which focuses on how they would train together and learn from each other's unique abilities.
Well, Saitama All Fiction could potentially refer to a fan - created idea that emphasizes Saitama's ability to be above all the normal rules of the fictional One Punch Man universe. For example, his strength is so overwhelming that it's like he exists in a realm of his own, where the typical limitations of the story don't really apply to him. He can defeat any foe with just one punch, and this 'All Fiction' concept might be an attempt to explain how and why he's so powerful in such a ridiculous way.
Saitama's speed in the manga is incredibly fast. It's hard to put a specific number on it, but he can cover great distances in no time and react with lightning speed to any threat.