One idea could be that the OC Salvatore has a unique power, like the ability to control time briefly. They use this power to outwit Katherine Pierce in a battle of wits and strength. Maybe they are fighting over a powerful magical artifact that Katherine wants to use for her own evil purposes.
Well, perhaps the OC Salvatore is actually a long - lost relative of the Salvatores, but with a different moral compass. In the fanfic, they face off against Katherine because she has wronged their family in some way in the past. The OC could have some special knowledge about Katherine's weaknesses that they use to their advantage during the confrontation.
A possible plot could be that the OC Salvatore has made a deal with some other supernatural beings to gain enough power to take on Katherine. They have different fighting styles. The OC might be more of a strategist, while Katherine is more impulsive. The fanfic could explore how their different approaches play out in their battles and how the OC ultimately tries to defeat Katherine.
Well, the OC could be a vampire created by Katherine herself long ago but forgotten. When they meet again, the OC is torn between loyalty to Katherine and a newfound sense of right and wrong influenced by the Salvatores. Maybe the OC has the ability to read minds, which makes them a valuable asset in the battle against Katherine as they can anticipate her moves. Also, the OC could be from a different dimension where the rules of vampirism are different, and they bring this new knowledge to deal with Katherine, who is intrigued by their other - worldly powers.
In my opinion, if the OC Salvatore has been training specifically to take on Katherine and has some sort of unique advantage, like immunity to her mind - control tricks, then the OC might win. However, Katherine is not one to go down easily. She has survived for centuries by being smart and adaptable. If the OC makes a single mistake, Katherine could turn the tables on them. So it's really a toss - up between their powers, skills, and the situation in the fanfic.
The OC should have flaws as well as strengths. For instance, they might be overly impulsive, which often gets them into trouble but also makes them brave in the face of danger. Their backstory could involve being part of a secret society that was wiped out by Katherine, giving them a personal vendetta. In terms of appearance, give them a signature style of dressing, like always wearing a leather jacket with a specific symbol on it. This makes them stand out. And when it comes to their dialogue, make it full of spunk and determination, showing their strong - willed nature.
Another plot idea is that the Salvatore sister is forced to team up with Katherine. Perhaps there's a new, powerful enemy in town that only their combined knowledge and powers can defeat. As they work together, the sister starts to see Katherine in a different light, not just as the villain the Salvatores always thought she was. This could create a complex relationship full of tension and unexpected alliances.
One idea could be that the OC is a powerful witch who gets caught in the middle of the Salvatore - Rebekah drama. She might initially befriend Rebekah, not knowing her full vampire nature, and then fall for one of the Salvatores. This creates a love triangle full of supernatural twists.
A common theme is love triangles. Since Katherine has a history with the Salvatores, an OC as their sister can easily get caught up in the complex web of emotions. For example, she might be in love with someone one of the Salvatores also has feelings for.
Maybe an OC who is a scientist in both universes. They accidentally create a device that merges some of the characters' powers in unexpected ways. This leads to a series of adventures where they have to deal with the consequences, like a new villain emerging who has a jumbled set of powers. The OC then has to team up with some well - known characters to fix the situation.
Well, Archive of Our Own (AO3) is also a great source. It has a large collection of fanfics. To find 'oc salvatore sister katherine fanfic', you might start by typing in the full phrase in the search bar. Then, look through the summaries and tags of the stories that come up. Some might be about an original character who is related to the Salvatores and has some sort of connection with Katherine, whether it's a rivalry or an alliance.
One great 'Katherine Pierce Fanfic' is 'The Darker Side of Katherine'. It delves deep into her complex character, exploring her past and her relationships in a really interesting way. The author does a wonderful job of staying true to her personality as we know it from the show.
A good 'Katherine Pierce Fanfic' should first and foremost capture her essence. She's a complex, manipulative, and yet somewhat sympathetic character. So, the story should reflect that. For example, it could explore her reasons for her actions in the original series.