In a fanfiction where Naruto kills the Akatsuki, it could lead to a much more peaceful ninja world much sooner. The Akatsuki's plan to capture the tailed beasts was a huge source of unrest. With them out of the picture, the villages might not be as paranoid about security. However, it could also lead to new problems. The power vacuum left by the Akatsuki could be filled by other evil forces or there could be internal power struggles within the villages that were previously united against the Akatsuki threat.
In this fanfiction scenario, Naruto killing the Uchiha clan would make him an outcast in Konoha. The village that once supported him would turn against him. This could lead to Naruto leaving the village and becoming a rogue ninja. He might then form his own group of allies who believe in his cause, whatever that might be in this altered story. It would also change how the Akatsuki views Konoha. Instead of targeting Sasuke, they might target Naruto directly as the one who eliminated the powerful Uchiha clan.
For such a plot to be possible in the fanfiction, it could involve some major changes in the Naruto world. The Akatsuki could have some new secret weapons or techniques. Also, Naruto might be in a situation where he is not able to access his full power, like being poisoned or something. And perhaps the Akatsuki are more united and desperate than ever to achieve their goals, leading them to take out Naruto who is a major obstacle for them.
Yes, it can be quite a common theme. Many Naruto fans like to explore the idea of Naruto taking on the powerful Akatsuki members and defeating them in their own fan - created stories. It allows for a lot of creative freedom in terms of the battles, the power - ups Naruto might get, and the overall plot development.
Well, perhaps in the fanfiction, Naruto kills Orochimaru and the Akatsuki, but it turns out that Orochimaru had a failsafe. His death triggers a powerful curse that starts to affect Naruto and the Hidden Leaf Village. Naruto then has to find a way to break this curse while also dealing with the remaining threats that were associated with the Akatsuki. It could be a race against time to save the village and himself.
The most obvious consequence would be chaos. Naruto was the hope for the village. His death would likely lead to a great sense of despair among the villagers. Konoha might lose its strength and confidence.
One popular plot device is the power - up. Naruto might gain a new form or a super - powerful jutsu right before facing an Akatsuki member. Another is the betrayal within the Akatsuki. For example, someone in the Akatsuki might give Naruto information to help him in the fight. And the 'damsel in distress' can also be used, like Naruto has to save a friend from an Akatsuki member, which leads to the fight and the kill.
As a fan of web novels, my answer didn't completely fit the plot of Naruto novels. In Naruto novels, the female protagonist would not directly participate in the activities of the organization but would fight against the organization with other characters. If you have any questions regarding the plot of Naruto novels, I will be very happy to help you.
Sakura would probably be shocked. She knew the Akatsuki was powerful, and Naruto killing them all might make her see Naruto in a whole new light, perhaps as a more dangerous or powerful figure than she initially thought. Kakashi, on the other hand, might be worried about the implications. He would be proud of Naruto's strength but also concerned about the power vacuum and how it could affect the balance of the ninja world.
Perhaps the Akatsuki saves Naruto because they want to use him for their own purposes in a different way. Instead of killing him or using him as a weapon against Konoha in the traditional sense, they might save him from a situation where he is being hunted by other forces. Then they plan to train him or manipulate him in a new way to further their own goals, like changing the power structure of the ninja world.
One possible plot could be Naruto joining the Akatsuki under some false pretense. Maybe he's trying to infiltrate them to gather intelligence for the Leaf Village. He'd have to keep his true identity and motives hidden while interacting with the dangerous members like Itachi and Kisame.