A villain like Shigaraki would likely be interested in the power levels in the MCU fanfiction. He's always looking for ways to increase his own power, and seeing the various powerful artifacts and abilities in the MCU might give him some ideas. He could think about how he could use similar things in his own plans to take over the MHA world.
Sukuna does die in the manga. The way it happens is quite dramatic and ties in with many other elements of the story, adding depth and tension to the overall narrative.
She might be initially scared but quickly regain her composure. Uraraka is a brave character. She would likely start looking for ways to escape, using her zero - gravity quirk to her advantage, like floating up to vents or disabling the villains' weapons if she can.
Shigaraki would likely be disgusted if the fanfic made him seem weak or less of a threat. He'd probably scratch at his neck in irritation. Dabi would be dismissive. He'd think fanfics are just a waste of time and not worthy of his attention. Toga, though, might be intrigued. If the fanfic had a lot of blood and gore in it, or if it focused on her relationships in an interesting way, she could be really into it.
They might get angry if the fanfiction shows the heroes in a very positive light and the villains as weak or stupid. They have their pride and don't like to be made fun of or belittled, even in fan - made stories.
No. Ryomen Sukuna is a fictional character from Japanese mythology and modern manga/anime. He doesn't have a basis in a true historical event or person.
Nope. Ryomen Sukuna has no basis in reality. It's a product of the creative minds of the writers and illustrators who designed a captivating fictional character for the enjoyment of the audience.