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.
In the original work of " Celebrating Years," the Eldest Princess Li Yunrui instructed Si Lili to kill Fan Xian.
Si Lili was a spy in Northern Qi and the top star of Drunken Immortal Residence. She had been arranged by the Qing Emperor to stay by Fan Xian's side. In order to avenge Lin Gong and sabotage Fan Xian's mission to Northern Qi, Li Yunrui bribed Si Lili to poison the wine, wanting Fan Xian to die in Northern Qi.
According to reference 1 and 3, the Second Prince had ordered Lin Token to kill Fan Xian, but Wan 'er did not know. During Fan Xian's wedding, the Second Prince had told Wan 'er of Lin Token:1841Token:375's death, attempting to make Wan' er kill Fan Xian in anger.
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.
I'm not sure specifically as there could be many interpretations in fanfiction. It might involve Itachi and Sakura in a situation where they are somehow related to the concept of 'killing your heroes'. Maybe it's about challenging the ideals or figures they once looked up to.
In " Dragon Clan ", Lu Mingfei sacrificed his life to deal with the King of Earth and Mountain. The plot of the story entered a broader world, including more complicated interpersonal relationships, more massive wars, power struggles, and so on. In this world, the conflict between the dragons and the humans became more intense, and Lu Mingfei became a stronger leader, leading the war between the humans and the dragons in a brighter direction. However, even if everything was resolved, it did not mean that the story was over. It represented the beginning of a new story.
Yes, there are likely such fanfictions. Many fanfiction writers like to explore the idea of Itachi coming back to life with his memories intact. This allows for interesting character interactions, especially with Naruto. Itachi could use his wisdom and skills once again, and his relationship with Naruto could further develop in new and unexpected ways.