Well, there's the trope of the 'outsider villain'. This is an OC villain who doesn't fit into the normal hero - villain dynamic in the 'Boku no Hero Academia' world. They might have a completely different view on how things should be. Then there's the 'sympathetic villain' trope. Despite being a villain, the writer makes the readers feel sorry for them because of their past or current situation. Also, the 'mastermind villain' who is always one step ahead of the heroes is a common one.
First, develop a unique and interesting villain character. Think about their backstory, motives, and quirks. For example, a villain who was once a hero trainee but turned bad due to a tragic event. Then, create a compelling plot that involves the villain's actions and how they interact with the existing heroes in the 'Boku no Hero Academia' world. Also, pay attention to the writing style, keep it engaging and descriptive.
One common theme is the corruption of the hero system. These fanfics often show Deku turning into a villain because he sees the flaws in how heroes operate. Another theme is the exploration of good and evil. It makes readers think about whether Deku is truly evil or if he has valid reasons for his actions.
In a Deku villain fanfic, perhaps Deku could form an alliance with some of the existing villains in the Boku no Hero Academia world. He might see potential in them that the heroes overlook. He could team up with Shigaraki, believing that together they could reshape the world into a more 'fair' place, according to his now - twisted view.
An interesting concept for a 'boku no hero academia oc fanfic' is an OC who is a villain at first but then slowly realizes the error of their ways. Their quirk could be something that is initially seen as very menacing, like the power to steal the quirks of others temporarily. As the story progresses, they could start using this quirk for good, like helping heroes regain their lost quirks in battles against stronger villains.
Frustration could be a major motive. He has faced so much hardship in his journey to become a hero, from not having an initial quirk to being constantly put down. This built - up resentment could turn him into a villain.
One idea could be to create an OC vigilante who has a unique quirk that's not very flashy but extremely useful in stealth situations, like the ability to blend into shadows completely. This would add an interesting dynamic as they could move around unnoticed by villains and even some heroes. Another idea is to have the OC vigilante be from a family with a bad reputation in the hero world, so they have to fight against the stigma while trying to do good.
The theme of overcoming obstacles is very common. In these fanfictions, the lesbian couple has to overcome various obstacles like discrimination from other students or even some of the teachers. They also have to deal with the challenges of being heroes at the same time. For instance, they might have to hide their relationship while on a joint mission to avoid negative reactions from their teammates. This creates a lot of tension and drama in the story, which is a key part of many of these fanfictions.
One common theme is Nejire's growth as a hero. Since she's a character with a lot of potential in the original series, fanfics often explore how she hones her skills.
Power is a common theme. Since Redestro is a powerful character, many fanfics explore how he wields his power, whether for good or bad. Another theme is leadership, as he is a leader in the story. Fanfics often show different aspects of his leadership style.
One common trope is the 'outcast - turned - villain'. Your self - insert character might start as someone rejected by society or the hero system, and then decides to use their powers against it. Another is the 'secret - identity' trope. Your villain self - insert could have a normal life on the surface while secretly plotting villainous deeds. And the 'redemption arc' can also be a trope, where the villain self - insert realizes the error of their ways and tries to turn good.