One idea could be that Ichigo, through some sort of interdimensional rift, ends up in the Avatar world of Legend of Korra. He could initially be seen as a threat due to his otherworldly powers. But as the story progresses, he teams up with Korra to fight a common enemy that is trying to take over both their worlds. His Soul Reaper powers could be used in unique ways, like using his Getsuga Tenshou to blast away dark spirits that are plaguing the Avatar world.
One idea could be a story where Naruto and Korra meet in a dimension where the worlds of their respective shows collide. They could team up to fight a new, powerful enemy that threatens both their universes. Another idea is a time - travel story where Korra goes back in time to the Naruto era and has to adapt to the different ninja world while also sharing her bending knowledge.
One idea could be that the reincarnated character has memories of their past life. They could use this knowledge to predict events in the Avatar world. For example, they might know about an upcoming threat and start preparing for it much earlier than anyone else. This could lead to some interesting interactions with Korra and the other characters as they try to convince them of the danger.
Ichigo's Soul Reaper powers are based on spiritual energy, and Korra's bending is based on her connection to the elements. Their powers could interact in a way that creates a new form of energy. For example, when Ichigo uses his Getsuga Tenshou near Korra while she's bending, it might create a shockwave that combines the force of the spiritual energy blast with the element she's bending. This could be a very powerful and unique combination that they could use to defeat enemies.
For Legend of Korra fanfiction, you could write about an alternate universe where the Avatar cycle is broken. Korra has to figure out how to fix it while dealing with the chaos that ensues. You might also consider a story where Korra forms an unexpected alliance with a group of non - benders who have developed their own form of combat to rival bending. Additionally, a fanfic that delves into the relationship between Korra and Asami in more depth, showing their daily lives and how they contribute to the rebuilding of Republic City together, would be really engaging.
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.
A crossover might involve Hollow Ichigo being drawn to the Avatar state. He could sense the immense power within Korra when she enters the Avatar state and be both intrigued and threatened by it. This could lead to a series of battles and power struggles. Or perhaps some of the villains in Legend of Korra might try to team up with Hollow Ichigo, thinking his power could help them achieve their goals, but in reality, he has his own agenda and would double - cross them at the first opportunity.
One idea could be a crossover with another popular fantasy world like 'Harry Potter'. Korra could end up at Hogwarts and have to deal with magic in a completely new way. Maybe she'd use her bending to enhance or counter some spells.
One idea could be a crossover where Naruto, with the power of the Kyuubi, somehow ends up in the world of Legend of Korra. He could team up with Korra to face a new threat that combines the dark jutsu from Naruto's world and the bending abilities in Korra's world.
One possible plot idea could be a crossover where characters from Naruto and Legend of Korra have to team up to face the Juubi. Maybe the Avatar from Legend of Korra discovers a new power that is linked to the chakra of the Juubi in the Naruto world.
An interesting Legend of Korra OC fanfiction idea could involve an OC who was born with the ability to control spirits directly, without the need for Avatar - like mediation. This OC could face challenges as people fear their power. Also, an OC that is a bender who has lost their bending due to some accident and has to find a new way to be useful in the world of bending. Maybe they become a great teacher, teaching non - benders how to defend themselves against benders. And then there could be an OC who is a descendant of an ancient civilization and has access to forgotten bending knowledge.