In a fanfiction setting where Naruto's Rinnegan exists in the DC Universe, one of the most interesting aspects could be the sharing of knowledge. The Rinnegan is often associated with a deep understanding of the world in Naruto. In DC, a character with the Rinnegan might gain insights into the workings of the multiverse, similar to how Doctor Strange in the Marvel Universe has knowledge of different dimensions. This could lead to some really cool crossovers and interactions with DC's more magically - inclined characters like Zatanna or Constantine.
If a DC character got Naruto's Rinnegan in fanfiction, it would completely change their power dynamic. Take Batman for example. He's a highly skilled detective and martial artist, but with the Rinnegan, he could gain the ability to see the chakra or energy of his enemies. This would give him an edge in combat and investigations that he didn't have before.
It would change it a great deal. His red hair might make him stand out even more, and with the Rinnegan, his power level would be off the charts. Enemies might be more afraid of him, and allies might look at him with a new level of respect or suspicion. The power dynamics in battles would be completely different. For example, he could use the Rinnegan's abilities in ways that no one has seen before, changing the strategies of both his side and the enemy's side in wars and skirmishes.
It could change the political situation in the Naruto universe as well. A ninja with Rinnegan and Jiongu might be seen as a threat by the existing ninja villages. This could lead to new alliances and rivalries. Also, the way ninja are trained might change as the villages try to figure out ways to counter such a powerful combination. Moreover, the study of ninjutsu and kekkei genkai could be revolutionized as scholars try to understand the nature of these combined powers.
Naruto could be a mentor - like figure. His experience with different types of combat and his rinnegan - enhanced perception would allow him to guide the RWBY characters in battles. He might help Ruby improve her scythe - wielding skills by teaching her some of his sword - fighting techniques that he learned from Sasuke.
The plot might involve Naruto trying to find a way back to his own universe while getting involved in the affairs of the DC Universe. He could use his ninjutsu to fight against supervillains. Also, his immortality would give him an edge in long - drawn battles and he could form interesting relationships with DC characters like Batman, who might be intrigued by his abilities.
One challenge is balancing the power levels. Naruto has his own set of powerful abilities like the Rasengan and Sage Mode, while DC characters have super - strength, flight, and various other powers. Making sure that neither side overshadows the other can be difficult. For instance, if Naruto is made too powerful, it can make the DC heroes seem useless. On the other hand, if the DC characters are too overpowered, Naruto's unique abilities won't stand out.
Superman is also popular in these fanfictions. The contrast between his god - like powers and Naruto's more hard - earned ninja powers makes for an interesting dynamic. Also, characters like Wonder Woman are popular as they can have interesting interactions with Naruto, especially in terms of their different views on justice and heroism.
One interesting Naruto DC Universe fanfiction could be where Naruto has the powers of a Kryptonian. He uses his speed and strength in a way similar to Superman but with his own ninja - like twists. For example, he might use his chakra to enhance his heat vision or freeze - breath abilities.
In a fanfiction, if Naruto characters with Rinnegan entered the Fairy Tail universe, there could be a power struggle. Some Fairy Tail guilds might see them as a threat and try to drive them out, while others might see an opportunity to learn from their unique powers. The Rinnegan - holders could also form alliances with certain wizards, leading to new story arcs and adventures as they explore this new magical world together.