One common theme is the clash of cultures. Since it's a crossover, Madara from his original world has to deal with different cultural aspects in the new crossovers. Another theme is power struggle. Madara is often a very powerful character, and when he is reborn into new settings, there's often a struggle for power between him and the existing power structures in those worlds.
One idea could be a Madara crossover with the Naruto modern world. Imagine Madara suddenly appearing in a bustling city, confused by modern technology like cars and skyscrapers. Another could be a crossover with a fantasy world like Middle - earth from 'The Lord of the Rings'. Madara's powerful jutsu and combat skills would make for an interesting dynamic against the orcs and wizards there. Or perhaps a crossover with the Bleach universe, where he could face off against the Soul Reapers and Hollows.
Begin by choosing a world for the crossover. If it's the Final Fantasy world, study its magic systems, the different kingdoms, and the races. For Madara, think about how his Sharingan would interact with the crystal - based magic in Final Fantasy. After that, outline your story. You can start with a prologue that sets the stage for the crossover, perhaps showing a glimpse of Madara's life in the Naruto world before the event. As you write, focus on building a connection between Madara and the new world. Describe his reactions to the new environment, the people, and the powers that exist there.
One idea could be a crossover with the Harry Potter universe. Madara Uchiha could be a powerful dark wizard from a far - off land who arrives at Hogwarts. He might be intrigued by the magic there and try to either conquer or learn from it. Another idea is a crossover with the DC universe. He could be pitted against Superman, and his Sharingan powers would make for an interesting battle against the Man of Steel. He might also form an alliance with Lex Luthor, thinking they have similar goals of power and domination.
In a crossover with the Avengers, Thor would be an interesting character to pair with Madara. Thor has his godly powers and Mjolnir, while Madara has his Sharingan and immense combat skills. The clash between Thor's lightning and Madara's fire - based jutsu would be epic. Another good pairing could be with Batman. Batman's strategic mind against Madara's cunning and power would make for a great dynamic. Batman would have to rely on his gadgets and intelligence to outwit Madara.
A 'godlike Madara' in a crossover fanfiction could be really interesting. It might involve Madara from Naruto being given 'godlike' powers and then being crossed over into another universe, like a different anime or even a fictional world from a game. This could lead to some really epic battles and unique storylines.
One popular'madara reborn crossover fanfic' is 'Madara in the Modern World'. It has an interesting plot where Madara is reborn into a modern setting and has to adapt to new technologies and social norms. Another is 'Madara and the Magical Crossover' which combines elements of magic from different fictional universes with Madara's character.
Madara would have to adapt to the different threats in RWBY, mainly the Grimm. In his world, he was used to fighting other shinobi and clans. The Grimm are a whole new type of enemy. However, his Sharingan would give him an advantage in detecting their movements. He might also try to find a way to use the Grimm's negative energy, similar to how he used negative emotions in his own world to fuel his power.
Power struggle is a common theme. Since Madara is a very powerful character, when he is crossed over into other anime worlds, there's often a question of how his power will be received and how he'll deal with other powerful entities. For example, in crossovers with Dragon Ball Z, his power level is compared to the Saiyans.
Well, a really interesting madara crossover fanfiction idea could be a crossover with the Bleach universe. Picture Madara in the Soul Society, interacting with the Soul Reapers. He could be mistaken for an extremely powerful Hollow at first, and then the story could unfold as he tries to find his way back to his own world or decides to explore this new realm of existence. It would be full of action and interesting character interactions.