The other ninja villages would react with a combination of awe and fear. Awe because Naruto was able to take out such a powerful group single - handedly, but fear because they don't know what this means for the future. Will Naruto use this power to dominate? Or will he continue to strive for peace? Some villages might try to form alliances with Konoha out of fear or respect, while others might start to secretly plot against Naruto and Konoha in case he becomes a tyrant.
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.
Sakura would probably be very surprised and might feel a bit of jealousy if she has some lingering feelings for Naruto. She could act cold towards Ino or Naruto for a while. Shikamaru, being Ino's friend, might tease her about it a lot, but also be a bit protective. Choji would likely be more concerned about how Ino feels and might offer her some snacks to cheer her up if she's flustered.
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.
The Hidden Leaf villagers would be shocked. They see Akatsuki as the enemy, so they would think Naruto and Sasuke have betrayed them. Kakashi would probably be very concerned and try to find out their reasons. Sakura would be heartbroken and might even try to go after them to bring them back. As for the Akatsuki members themselves, some might be suspicious of Naruto and Sasuke's motives at first, while others might see it as an opportunity to use their power for Akatsuki's goals.
The Akatsuki members themselves would have mixed reactions. Some might welcome Naruto as a powerful addition to their ranks, seeing his potential. Others might be suspicious of his motives, especially those who are more hardcore in their anti - Leaf Village stance. And for the other Allied Shinobi Forces, they would see Naruto as a major threat now, changing the entire power dynamic in the ninja world.
The MHA characters' reactions could vary widely. For instance, All Might might see the Naruto fanfiction as a great source of inspiration. He could admire the way the characters in Naruto strive for their goals, just like heroes in their own world. Todoroki might be a bit detached but still interested. He'd analyze how the power systems in Naruto compare to quirks in their world. Mineta would probably be more interested in any fan service - like elements if there were any, but that's not a very positive reaction. Overall, it really depends on each character's personality.
Sasuke would be extremely angry. He and Naruto had a complex relationship that evolved from rivalry to friendship. His first reaction would likely be to seek vengeance. Kakashi himself would be filled with guilt and self - loathing. He has always been Naruto's teacher and protector in a sense. Hinata would be heartbroken. She had deep feelings for Naruto. The rest of the village would be in shock and disbelief. Naruto was seen as their future, and his sudden death at Kakashi's hands would create a sense of despair and confusion.
Bakugo Katsuki, on the other hand, might be more dismissive at first. He'd think it's all just some made - up nonsense that has nothing to do with real hero work. But if he found a fanfiction that had an interesting battle scenario or a strong - willed character, he might grudgingly admit it had some merit. He'd probably scoff at any overly emotional or sappy parts though.
Other characters such as Rex might see it as a sign that the fight against the Empire has truly corrupted Ezra. He would be disappointed as he has seen the potential for good in Ezra. And for new allies or characters in the fanfiction, they would be very cautious around Ezra. It would create a sense of unease and fear among the rebellion. The event would not only affect the personal relationships but also the overall morale and unity of the rebel forces.
Sakura would be devastated. She has always had deep feelings for Sasuke. She might initially be angry with Naruto, thinking that there could have been another way. But later, she might understand Naruto's difficult decision when she realizes the threat Sasuke posed.
For Kakashi, it would be like losing his student all over again. He has trained Naruto and seen his growth. His death would make Kakashi question his own role as a teacher and mentor. He might become more withdrawn and blame himself for not being able to prevent Naruto's suicide.