In a fanfic where Naruto gets killed by Pain, it's a dark turn of events. The story would then likely focus on how the remaining characters cope. For example, Kakashi might feel a great sense of guilt for not being able to protect Naruto. Hinata would be heartbroken. Moreover, the Nine - Tails would be left without a host, which could also lead to all sorts of problems. The ninja world would lose its most prominent symbol of perseverance and friendship, and it would be a very different world from the one we know in the original Naruto story.
One possible scenario could be a power imbalance. Maybe Sasuke discovers some new, extremely powerful jutsu that Naruto has no defense against. For example, a jutsu that can nullify Naruto's chakra or attack his spirit directly. Another possibility is a miscommunication or a breakdown in their relationship. If Sasuke believes Naruto has betrayed him in some way, his anger could lead him to kill Naruto. However, this goes against the core of their bond in the original series.
Naruto would be shattered. Given his strong sense of justice and his connection to Hinata, whether it's a romantic or platonic one. He would initially be numbed by the shock. But soon, his emotions would erupt. He could go through different stages, from mourning and self - blame (thinking he could have protected her) to a fierce determination to make things right. His actions would be driven by his love and respect for Hinata, and he would not rest until he has either avenged her or found a way to bring her back, if possible.
If Naruto gets killed in a fanfiction, the storyline would change drastically. Konoha would lose its most powerful shinobi and its symbol of hope. His friends like Sasuke, Sakura, and Kakashi would be deeply affected. Sasuke might go on a rampage seeking revenge. The village would be in a state of shock and mourning, and its defenses would be weakened. Enemies might see this as an opportunity to attack.
A plot could revolve around the power vacuum left by Naruto. The Leaf Village is in disarray, and other villages start to make moves against it. Pain might realize that killing Naruto wasn't really what he wanted in the long run, as it led to more instability. Or maybe a character who was in the background in the original story steps up to try and fill Naruto's shoes. They struggle to gain the respect and power that Naruto had, while also dealing with the grief of his loss.
His friends would be devastated. Sakura, who has known Naruto for a long time, would be heartbroken. She might lose her motivation to be a strong kunoichi. Sasuke, despite his complicated relationship with Naruto, would feel a great sense of loss. He might blame himself for not being there to protect Naruto. And Kakashi would feel like he failed as a mentor. They would all have to deal with grief and at the same time, step up to protect Konoha in Naruto's absence.
Well, it could lead to chaos in the Hidden Leaf. His friends like Sasuke might go on a vengeful rampage. They would be filled with rage and guilt, thinking they could have prevented it. The village would also be in turmoil, as Naruto was their hero and a symbol of hope.
Well, Sasuke would be furious. Naruto was his rival and also his friend. He would seek vengeance on the mob without a second thought. Shikamaru, on the other hand, would be more calculating. He would try to figure out how such a thing could happen and what the long - term consequences for the village would be.
The story could develop in a very dark direction. Sasuke might be filled with regret immediately after killing Naruto. This could lead to him isolating himself from the rest of the ninja world as he grapples with his actions. The ninja villages might be in chaos as Naruto was seen as a symbol of hope. Without him, there could be power struggles among different groups.
Hinata would be devastated. She has always had deep feelings for Naruto. She might lose all hope and become a shell of her former self. Also, Kakashi would feel a great sense of guilt. He was Naruto's teacher and protector in a way. He would probably question his own abilities and actions that led to this situation. And for the village as a whole, it would soon realize the mistake they made when they face new threats without Naruto to protect them.