In some fanfics, Naruto might team up with unexpected characters to defeat Pain. For example, he could join forces with Orochimaru. Orochimaru, with his knowledge of jutsus and dark arts, and Naruto, with his brute strength and positive energy, create a unique combination that outsmarts Pain's abilities.
One unlikely ally could be Zetsu. Zetsu is usually seen as a villain, but in a fanfic, he could have his own motives for helping Naruto defeat Pain. Maybe he wants to disrupt the Akatsuki's plans from the inside and sees Naruto as a useful tool for that.
Another plot twist might be that Pain has a hidden motive for attacking Konoha that is completely different from what was originally thought. And Naruto, in the process of defeating him, uncovers this truth. For example, Pain could be under the control of a more powerful enemy who wants to test Konoha's defenses through Pain's attack, and Naruto has to deal with this new revelation as well as defeat Pain.
Social media groups focused on Naruto can also be a good source. For example, on Facebook or Reddit, there are groups dedicated to Naruto. Members of these groups might discuss and share fanfictions they like. You can post a request for 'Naruto defeats Pain' fanfictions and see what kind of responses you get.
Often, Naruto's relationships with other characters are explored further. He might have deeper conversations with Sasuke, trying to convince him to come back to the village for good. His bond with Sakura could also develop in different ways, perhaps becoming a stronger friendship or even something more romantic in some fanfictions.
In some fanfictions, after Naruto defeated Pain, the village started to rebuild immediately. Naruto became a hero not only in name but also in the hearts of every villager. People looked at him with newfound respect and admiration.
In a 'naruto after pain fanfic', Naruto is key. However, characters like Tsunade are important too. She can lead the medical and administrative aspects of the village's recovery. Then there are Naruto's friends like Kiba and Choji. They can help with the physical tasks of rebuilding, and also in the security patrols around the village to prevent any new threats.
Naruto could also be more focused. The experience of the Pain invasion made him realize the importance of being fully present and concentrated during battles and training. He might have less of his usual goofiness and be more serious about his growth as a shinobi.
Well, in a fanfic anything can be possible. Naruto has his own set of powerful jutsu like the Rasengan and Shadow Clone Jutsu. The Justice League members also have their unique powers. But if the writer of the fanfic wants Naruto to win, they can create scenarios where Naruto's speed, strategy, and chakra powers outwit the JL. For example, Naruto could use his clones to confuse Superman while using a Rasengan to take him out. Then he could use his shadow clones to distract Batman and use his chakra control to disable Cyborg's systems. It really depends on how the fanfic is written.