Well, there are also those characters who might be a bit shocked or confused. Take Levi from Attack on Titan. He's a very serious and no - nonsense type of character. If he were to read some of the fanfic about him that deviated too much from his own self - perception, like being made into a comical or overly emotional character in the fanfic, he might be taken aback at first. But then he might also realize it's just a different interpretation and not take it too seriously.
There are also cases where Shouto could be in shock. The suddenness of the kidnapping could leave him stunned for a while. During this time, Dabi could have the upper hand. But as Shouto recovers, his natural instincts as a hero trainee kick in, and he starts to think of ways to get free and stop Dabi's plan, whatever it may be.
Well, it depends on the nature of the fanfiction. Some anime characters might be amused if the fanfiction is light - hearted and full of comical situations. For example, if it's a fanfic about a cooking competition among the characters from a shonen anime, they might react with good - natured laughter and competitiveness. They could also be confused if the fanfiction takes their story in a very strange or unexpected direction, like suddenly making a character from a historical anime end up in a space adventure.
Hawks is a great character to pair with Dabi in fanfic. Their relationship in the original story is complex and full of tension, which can be explored further in fan - made stories. There's also Shigaraki. Since they are both important members of the League of Villains, there's a lot of potential for interesting dynamics between them in fanfics.
Kakashi would be very observant. He would look for how the fanfiction writers understand the world of Naruto, the values and the moral lessons. He might even use some of the creative ideas from the fanfiction in his own teachings if he thought they were valuable and in line with the spirit of the original story.
There could be characters who are outraged. If the fanfiction distorts their personality or makes them do things completely against their nature, they may be very angry. For example, a noble character made to act like a coward in the fanfiction would likely not take it well.
They might be confused at first. RWBY has its own unique lore and concepts that are different from many anime. So anime characters may need time to understand things like Grimm and Huntsmen. For example, if Goku from Dragon Ball was watching, he'd probably be like 'What are these strange monsters?'.
They could be surprised. The fanfiction might show them in scenarios they never imagined, like a shy character being in a very bold and adventurous situation.
The heroes in MHA like All Might might view Dabi fanfiction with a sense of concern. All Might has always been about justice and the greater good. He might see Dabi fanfictions as a sign of how some people are attracted to the darker side of the hero - villain dynamic. He could worry that it might influence younger fans in the wrong way. However, villains in MHA might have different reactions. Shigaraki could see Dabi fanfictions as a way to understand how the public perceives Dabi and use that knowledge to his advantage in his evil plans.
They could be angry. Consider a character like Ichigo from Bleach. If the fanfiction makes him look weak or changes his character in a way that goes against his core values, he would likely be furious. After all, he has his pride as a Soul Reaper and a protector.