Perhaps a crossover with a post - apocalyptic world. Korra could use her bending skills to help the survivors in that desolate world. She might face challenges like finding clean water sources (using water bending) and building shelters (using earth bending). This would test her leadership and problem - solving skills in a completely different context.
A cool plot could involve a crossover with a modern-day superhero universe. Korra's bending powers would be a contrast to the high - tech gadgets of the superheroes. Maybe they team up to fight a common enemy that threatens both their worlds, like a powerful villain who wants to steal bending abilities for his own evil plans. It would be interesting to see how Korra's strong - willed and independent nature interacts with the more team - oriented superheroes.
One idea could be a crossover with another fantasy world where Korra has to learn new bending techniques from that world's magic users. This would bring a fresh dynamic as she struggles to adapt to different power systems.
One idea could be exploring the backstory of a minor character. For example, delving into the early life of a non - bender in Republic City and how they coped with living in a world where benders had more influence. Another idea is to create an alternate timeline where Korra fails to restore the balance and how the world descends into chaos as a result. Or perhaps a fanfiction centered around a new romance between two characters that were not paired in the original series.
One idea could be exploring Korra's life after she restores balance. Maybe she travels the world teaching the new generation about bending. Another could be a story where she has to face a new, unknown threat that challenges her in different ways than before.
For a Legend of Korra crossover fanfiction, a crossover with the Star Wars universe would be cool. Korra could be on a planet in the Star Wars galaxy and interact with Jedi and Sith. Her bending could be seen as a new form of 'Force - like' power. She might get involved in the struggle between the light and dark side. Also, a crossover with the world of Studio Ghibli. Korra could find herself in the beautiful and magical worlds created by Miyazaki, like in Spirited Away. She could use her bending to solve the problems in those unique settings.
One plot idea could be that your OC discovers a long - lost bending technique. This could attract the attention of both good and bad forces. For example, the Red Lotus might want to use it for their own purposes, while Korra and her friends would try to protect it. Another idea is that your OC is an ambassador from a small, previously unheard - of tribe. They come to Republic City to establish relations, but face many challenges due to cultural differences and political intrigue. Or perhaps your OC has a prophecy about the future of the Avatar world and has to convince everyone, including a skeptical Korra, that it's real.
Aang could be a great crossover character. Since he is from the previous Avatar cycle, his different approach to bending and his more laid - back personality compared to Korra could create interesting interactions. He could offer her wisdom from his own experiences as an Avatar.
One idea could be a struggle for power between Korra and the Dark Avatar. Korra, being the Avatar, has to fight against the Dark Avatar's malevolent plans to bring chaos to the world. Another could be a story where the Dark Avatar tries to corrupt Korra, using her insecurities against her.
One idea could be that the Avatar characters gain the ability to use magic when they enter the Harry Potter world. For example, Aang could use his airbending skills along with magic spells to fight against the Death Eaters. Another could be that Hogwarts students are sent to the Avatar world for a special exchange program, and they have to learn to bend elements instead of casting spells.
Maybe the Avatar, in his journey to master all the elements, travels to the Naruto world. He could learn some ninja techniques and incorporate them into his fighting style. The Avatar could also teach the ninja about the power of bending, which could lead to some really unique team - up strategies among the characters.
One idea could be to have the Voltron pilots end up in the Avatar world. They could learn bending techniques and use their Voltron skills in combination with them. For example, Keith's swordsmanship might blend well with waterbending moves in a fight.
One idea could be exploring Korra's early training days in more detail. Maybe she has a secret adventure during that time that wasn't shown in the original series. Another could be a fanfiction where Korra has to team up with an unexpected ally from the Spirit World to save Republic City from a new threat. A third idea is to write about what would happen if Korra lost her bending abilities for a while and had to learn to fight and defend without them.