I do not own the right to One Punch Man or Spider-man except for my own character.
This is his costume, just recolored. The original artist belongs to Paris Alleyne
His backstory will be a revealed little by little as the story progresses.
Regular Powers: Organic webs, sticks to walls, stingers, venom blast, spider-sense, super strength, flexibility, great endurance. Has a Cosmic form that's much like Cosmic Spider-man from the comics except when he fully transforms his red lenses and back spider logo glow white.
Cosmic powers: Infinite strength, infinite speed, infinite durability, flight, cosmic beams, nuclear blasts, reads minds if he chooses to, make his webs turn into Adamantium or Vibranium, structure his webs into anything his imagines, disable or increase someone's powers permanently or temporarily. Doesn't need to eat food, etc. Some of these abilities will be used and some won't.
His themes: I would go for the Danny Elfman's Spider-man theme since that's my personal favorite. Other music scores might be added to the story as well. Most will be emotional music.
Also some chapters will be around 1k to 7k words or higher.