In many fanfictions, Naruto might use new jutsus or a deeper understanding of his own power. Maybe he taps into a more powerful form of the Nine - Tails' chakra and combines it with his Sage Mode in a unique way to overpower Pain.
Well, in some versions, Naruto might use his new and improved Rasengan techniques. He could have combined it with his Sage Mode powers to overpower Orochimaru. Maybe he also uses his quick thinking and the element of surprise, since Orochimaru is always so full of his own schemes.
In some fanfictions, Naruto's pain might manifest through his actions. For example, he could become withdrawn and isolate himself from his friends. This is because Naruto has always been a social person, so any deviation from his normal behavior could be a sign of his internal pain.
He might put on a fake smile and act normal. Naruto is good at being energetic on the outside, so his family may not suspect that he's in pain.
He could feel it through a shared chakra link. Since they are related and Minato sealed the Nine - Tails in Naruto, there might be a latent connection that gets activated in the fanfiction, allowing him to sense Naruto's pain on a physical and emotional level.
In many fanfictions, Naruto might hide his pain by putting on a big smile. He's always been the type to try and be positive in the face of his friends. He could also distract others with his goofy antics, like making a joke or doing something silly to shift the focus away from his inner turmoil.
Fanfiction explores the relationship of the Naruto Pain Brothers in various ways. Some stories focus on their loyalty to each other. For example, in many fanfics, we see how they would sacrifice for one another. They are often depicted as having a deep, unbreakable bond that was formed through their shared experiences.
Well, Naruto could also seek support from his friends like Sasuke or Sakura. They have been through a lot together, and they might be able to offer him some comfort and advice on how to handle this difficult situation. Since Naruto values his friendships highly, their words could have a big impact on him.
One possible cause could be his sense of failure. Naruto always wants to protect his friends and village, so if he fails in a mission or is unable to save someone, it can cause him great pain.
Maybe it's some kind of special jutsu or a curse that backfires in a way that numbs his pain receptors. For example, a powerful sealing technique might have been placed on him accidentally or on purpose that has this side - effect.
The village might experience a huge boost in morale. Naruto killing Pain would be seen as a major victory, and the villagers would feel safer. They would look at Naruto as an even greater hero, which could lead to more trust and unity within the village.