First, you need to create a unique villain OC. Think about their backstory, what made them turn bad. For example, if they had a tragic childhood event like being bullied or abandoned. Then, consider their powers. It should be something that fits the MHA universe. Maybe a power related to shadows or mind control. Also, give them a distinct personality. Are they cold - hearted, or do they have a soft side? When writing the fanfiction, start with an interesting hook to draw readers in, like a mysterious crime scene caused by your villain OC.
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.
Well, in some 'villain watch mha fanfiction', the villains might watch the heroes' interactions with civilians. This could lead to different reactions among the villains. Some might see it as a weakness to exploit, while others might start to question their own motives when they see the positive impact the heroes have. It really depends on the creativity of the writer. There are also stories where the villains watch the heroes' internal conflicts, like Midoriya's struggle with his power, and use that psychological knowledge against them.
Some MHA characters might be flattered. For example, Midoriya would probably be really excited and take it as a sign of how much he's inspired people. He might even look for positive lessons in the fanfiction to improve himself.
If the MHA characters were to react to a Mastermind fanfiction, some would be more accepting than others. Characters like Ochaco might find it really exciting. She's a fan of the heroes herself, so seeing different takes in fanfiction would be like getting a new perspective on the MHA world. However, characters like Shoto, who are more reserved, might be a bit hesitant. He might need some time to process what he's reading. But overall, it would be a very interesting scenario as it would show how the characters view different interpretations of their world.
Some characters would be shocked. For example, if the fanfiction had a really dark and unexpected Mastermind plot, like a hero turning out to be the mastermind of all the villains' plans, characters like Tsuyu would be very taken aback. She'd probably question the motives behind such a plot. Then there are characters like Denki. He might be more into it if it had some cool action scenes in the fanfiction, regardless of how out - of - the - blue the Mastermind storyline was. And Nejire would probably be super curious about the emotional depth of the characters in the fanfiction.
You can try looking on Archive of Our Own (AO3). It has a large collection of My Hero Academia fanfiction, and you're likely to find some great 'villain watch' ones there.
In MHA villain OC fanfiction, a mistake is not giving the villain OC a clear motivation. Just being evil for the sake of it is boring. Their actions should be driven by something, like a desire for revenge or power. Don't make their design too outlandish that it doesn't seem like it belongs in the MHA world. And don't forget about character development. If the villain OC is just static throughout the story, it won't be engaging. They should grow or change in some way, even if it's a downward spiral into more evil.
The Quinx Squad could react with a mix of respect and wariness. They respect power, and Kaneki has a lot of it. However, they are also loyal to their cause of protecting humans from ghouls. Meeting Kaneki would force them to re - evaluate their views. They might start to question whether all ghouls are truly bad, especially when they see that Kaneki has his own moral code. This could create internal conflict within the squad as they try to figure out how to deal with Kaneki.
If it's a Disney fanfiction based on a princess story, the female characters in MHA like Momo Yaoyorozu might relate to the princesses' grace and leadership. Meanwhile, the male characters could either be in awe or a bit dismissive, depending on their personalities. For example, Todoroki might be quietly respectful, while Mineta might make some inappropriate remarks (if we're being honest about his character).