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.
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.
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.
One common element is Naruto's growth. He usually has to reach a new level of power or understanding to defeat Madara. For example, he might gain a new jutsu or a deeper connection with his inner chakra.
Another possibility is that Naruto could defeat Kakashi if the latter was in a weakened state. Maybe Kakashi had just come out of a tough battle with other powerful enemies and was low on chakra. Meanwhile, Naruto was at his peak, full of energy and ready to fight. In this situation, Naruto's sheer determination and his own strong abilities could lead to his victory.
In a more psychological approach, Naruto could have grown so much as a character that he no longer fears Kakashi's reputation. This new - found confidence could change the dynamics of their fight. He might be able to read Kakashi's moves better and anticipate his attacks. Combined with his own ever - improving skills, Naruto could defeat Kakashi in this state of mental superiority.
There are fanfictions where Naruto teams up with other powerful characters like Jiraiya. Together, they come up with a plan to trap Orochimaru and then Naruto delivers the final blow. Naruto might use his Sage Mode skills, if he has them in that particular fanfiction, in combination with Jiraiya's knowledge and power to outwit and defeat Orochimaru.