There could be a fanfiction where Klaus realizes his true feelings for Katherine after she saves his life. In this story, they might struggle with their past betrayals but eventually find a way to be together. Katherine's cunning nature might be softened by Klaus's affection, and they could have a complex relationship full of passion and drama.
One interesting Klaus fanfiction could be about his backstory before coming to Mystic Falls. It might explore his relationships with his family in more depth, like his complex bond with Elijah. Another could be a story where Klaus tries to redeem himself and form an unexpected alliance with the main characters. There are also fanfictions that focus on a romantic relationship between Klaus and a new character, adding a fresh twist to his character development.
There are fanfictions where Katherine has a change of heart and tries to redeem herself for Stefan. She could be fighting against her old nature and Stefan is initially skeptical but gradually starts to believe in her transformation. This would be a story full of internal and external conflicts as they navigate their relationship in this new dynamic.
One interesting fanfiction could be about Elijah trying to redeem Katherine. Maybe he sees a side of her that others don't, and he attempts to guide her towards a more positive path. It could involve them traveling together and facing various challenges from the vampire world.
One interesting fanfiction could be about Katherine and Elena teaming up against a common enemy. In this story, they might realize that despite their differences, their combined power is needed to defeat a new and powerful vampire in Mystic Falls. They start to train together and along the way, they learn more about each other's pasts and find some common ground.
There are fanfictions where Katherine returns from the dead in a different form, perhaps as a spirit. Damon, who has always had a deep connection with her, has to figure out how to interact with this new version of Katherine. It could involve a journey of self - discovery for Damon as he realizes that his feelings for her are more complex than he thought, even in this new and strange situation.
Another type of fanfiction could be a time - travel one. Stefan and Katherine are sent back in time to a period before Katherine was turned into a vampire. In this time, Stefan tries to prevent Katherine from becoming a vampire in the first place. This would change the whole course of their relationship and the events in the Vampire Diaries universe. It would be full of interesting twists as they navigate through the past, trying not to change too much but also trying to change their own fates.
One interesting fanfiction could be about Klaus and Caroline traveling the world together. In this story, they explore different cultures and face various challenges that bring them closer. For example, they might go to an ancient vampire coven in Europe and have to deal with the politics there while also deepening their relationship.
There might be a fanfiction where Jeremy gets trapped in a parallel world created by Klaus. In this world, Klaus is the only one who can help him get back home. Along the way, they have to face challenges together, and Jeremy discovers a different side of Klaus, a more vulnerable side that he never expected. This leads to a change in their relationship as they start to understand each other better.
Archive of Our Own (AO3) is also a popular platform. It has a well - organized tagging system. Just type in 'Klaus' and 'Katherine' from The Vampire Diaries, and you'll get a list of relevant fanfictions. The site also allows for more detailed filtering based on your preferences like length of the story, whether it's complete or in - progress etc.
Her unpredictability. You never really know what she's going to do next. In fanfiction, this allows for a lot of creative plot twists.