The power balance would be completely disrupted. Without the ninja villages, there would be no organized ninja forces. This could lead to smaller groups or individuals vying for power, causing chaos everywhere.
It could be Sasuke. If he were to turn to the dark side in the fanfiction, his Rinnegan powers could be used to destroy Konoha. He has the potential to be extremely powerful and if he has some sort of vendetta or is influenced by some dark force, he might take his anger out on the village.
Maybe Naruto gets some sort of dark power that makes him go berserk and start destroying everything in his path. For example, he could be influenced by an ancient evil curse.
It could be a new character that we haven't seen in the original Naruto series. This character might be jealous of Naruto's power and wants to see him destroy his own world so that he can take over the chaos that follows.
In this fanfiction scenario, Naruto might be able to destroy Sasuke during the Chunin Exams due to his own growth and newfound abilities. Maybe he has mastered a new jutsu that gives him an edge over Sasuke. For example, if Naruto has fully harnessed the power of the Nine - Tails at this point, his strength could be overwhelming.
Probably not. While there are a lot of Naruto and Fairy Tail fans out there, the idea of Naruto destroying Fairy Tail in a fanfiction is not something that is mainstream. Most fanfiction tends to focus on more positive interactions between different fictional worlds, like friendships or alliances. This concept of destruction might be a bit too dark or out - there for the general fanfiction - reading audience.
One possible plot could be Naruto using his new Sage of Six Paths powers to take on the Akatsuki one by one. He could start with Hidan and Kakuzu, quickly dispatching them with his enhanced speed and strength. Then, he moves on to Deidara, outmaneuvering his explosive attacks with his own agility. Another plot might involve Naruto infiltrating the Akatsuki's hideout alone, using his shadow clones as decoys. He could then surprise Pain and defeat him in an epic battle, showing his growth as a ninja.
In this kind of fanfiction, Naruto might be banished due to some false accusations or political conspiracies in Konoha. Once banished, he could decide to destroy Konoha out of anger and a sense of betrayal. He may have learned powerful jutsus during his exile and use them against the village that once rejected him.
It could be a fan - made concept where in a fanfiction Naruto somehow has a scenario where he destroys things related to Fairy Tail. Maybe it's a crossover idea where Naruto's powers are pitted against the world of Fairy Tail and he causes destruction within that fictional setting.
For Naruto, he would have to grapple with the fact that he is fighting his former friend. This could make him more solemn and determined. He might develop a darker side as he realizes the seriousness of stopping Sasuke. For Sasuke, he could start as overconfident in his power but as Naruto keeps pushing him back, he could become more desperate and start to question his own motives.