In many fanfictions, the scenario of Naruto and Itachi killing the Uchiha clan is a very interesting but also controversial topic. One aspect could be the change in Naruto's character. Usually, Naruto stands for justice and protecting others. If he were involved in such a massacre, it would be a huge deviation from his original character. Maybe in the fanfiction, there could be some extreme situations that force him to do so, like being mind - controlled or having some false information.
In some fanfictions, a possible motivation for Naruto could be to prevent a greater evil. Maybe he was tricked into believing that the Uchiha clan was about to start a war that would destroy the entire ninja world. So, he thought that by taking part in killing the clan, he could save more lives in the long run.
If Naruto saved the Uchiha clan, the story of the Hidden Leaf Village would be rewritten. The history of the Uchiha's massacre would no longer be a dark stain on the village's past. The Uchiha would contribute their unique skills and abilities to the village's development. For example, their Sharingan abilities could be used for better security or in battles against common enemies. There would also be a change in the relationships between characters. People who were once enemies of the Uchiha might have to learn to work with them.
One great Naruto and Itachi fanfiction is 'The Bond Beyond Clans'. It delves into a scenario where Naruto discovers a hidden side of Itachi's past that was not known before. It shows how their relationship could have developed in a different way, with Naruto having a deeper understanding of Itachi's sacrifices.
The village of Konoha would also be in turmoil. The Uchiha were an important part of the village. Their massacre by Naruto would create a huge rift among the villagers. Some might support Naruto, believing he had a good reason, while others would be horrified and demand justice. It could lead to a civil war within the village.
A reason could be that Itachi is framed as a traitor to the Leaf Village in the fanfiction. Naruto, being the defender of the Leaf, would then see Itachi as an enemy and take action to kill him to uphold the village's safety and honor.
One way Naruto could save the Uchiha clan in fanfiction is by using his influence. Naruto is highly respected in the village. He could convince the village elders to re - evaluate their treatment of the Uchiha. He might show them that the Uchiha were being wrongly persecuted and that there was a way to co - exist peacefully. He could also use his power as a Jinchuuriki to protect the Uchiha from any external threats that might be a factor in their downfall.
One common theme is redemption. Itachi, with his past actions, sees protecting Naruto as a way to redeem himself. For example, in many fics, he tries to make up for the wrongs he did to his clan by ensuring Naruto's safety, as Naruto represents hope for the village.
In some fanfictions, Naruto might have an Uchiha bloodline awakening due to some unforeseen circumstances. This could lead to him developing Sharingan-like powers that are different from the norm. For example, his Sharingan could have a unique ability related to his Uzumaki chakra, creating a whole new set of jutsus and combat styles for him.
Well, one possibility is that Naruto would be trained in the unique Uchiha techniques. He might learn how to use the Sharingan in ways that no one expected. Also, he could gain a new family within the Uchiha clan, which would change his whole perspective on life and belonging.