One idea could be an OC who discovers their psychokinesis quirk gradually. They start with small things like moving a pencil, then as they train, they can lift heavier objects. This can lead to an interesting story arc of self - discovery.
The OC could start as a shy and withdrawn character, afraid of their psychokinesis quirk. But as the story progresses, they gain confidence. For instance, at first, they might accidentally break things with their quirk and be scared, but later they learn to control it and become more self - assured.
One way is through self - sacrifice. If the character uses their evil quirk to save a lot of people at great personal cost, it could be a step towards redemption. For example, if their quirk is something like mind - control and they use it to stop a powerful villain who is about to destroy a city, but in the process they lose their own ability to use the quirk. Another way is by showing remorse and actively trying to make up for their past actions. They could start doing volunteer work in the community, using whatever skills they have (even if related to their quirk in a non - evil way) to help others.
To create a compelling OC with a sound quirk, start with the basics of the quirk. Decide on what exactly they can do with sound. Can they create sonic blasts? Or perhaps they can mimic any sound they've heard? Once you've nailed down the quirk, focus on the character's appearance. Maybe they have ears that are slightly larger to better pick up sounds. Their clothing could also be designed to enhance or control their quirk, like having sound - absorbing materials. In terms of personality, they might be confident because they know the power they hold, but also a bit lonely as not many people understand their quirk. And don't forget to give them goals. It could be something as simple as wanting to be accepted for who they are or as complex as using their quirk to change the world.
Often, there are original characters created specifically for the fanfiction. These OCs are the main focus with their dark quirks. There might also be some canon characters from the original work that the fanfiction is based on. They could be friends, foes or mentors to the OC. For example, if it's a fanfiction based on a superhero story, there could be a well - known hero who tries to help the OC control their dark quirk.
One possible plotline could be that the oc with the evil quirk tries to hide it from others at first. They might be afraid of being ostracized. For example, they could pretend to have a normal quirk in public but struggle internally with the dark impulses their evil quirk brings. Another plotline could involve the oc being forced to use their evil quirk for self - defense in a dangerous situation and then having to deal with the consequences of others seeing what they can really do. Maybe they get hunted down by heroes who misinterpret their actions as villainous.
One idea could be an OC with a sound quirk who can manipulate sound waves to create illusions. For example, in a battle, they make the enemy think there are multiple allies when it's just sound - based images. Another could be an OC that uses their sound quirk to communicate with animals, as different frequencies might be understood by them. A third plot idea is an OC with a sound quirk in a music - based society where their quirk gives them an edge in creating the most beautiful and powerful music, but they face jealousy from others who don't have such a useful quirk.
There could be a story where the OC's dark quirk is a secret at first. They are living a normal life until certain events start to trigger the quirk. The fanfiction might explore how they keep this secret from their friends and family. As the story progresses, they might be forced to reveal it when facing a powerful enemy that only their dark quirk can defeat. This could lead to a lot of drama, with their loved ones having to come to terms with this new side of the OC.
One idea could be to make the character with the lightning quirk have a fear of water. This would add an interesting dynamic as lightning and water don't mix well. They could struggle to control their quirk when near water, and it could be a source of internal conflict for them.
When writing action scenes for a character with a lightning quirk, describe the speed and intensity. For example, 'He shot out bolts of lightning, each one crackling through the air like a whip, their bright light blinding his opponents for a split second.'