Madara might discover Naruto's training with Jiraiya. The times they spent traveling together, and how Jiraiya taught Naruto not only powerful jutsu but also important life lessons. Also, Naruto's first Chunin Exams would be an important part of his past. There, he faced many challenges and opponents, and it was a major step in his growth as a ninja. It was during this time that he started to make more friends and allies.
Perhaps Madara would see Naruto's relationship with Sasuke. Their early rivalry that gradually turned into a deep bond. Naruto's determination to bring Sasuke back from the path of revenge was a major part of his emotional journey. Madara could also witness the times when Naruto tapped into the power of the Nine - Tails, especially during desperate battles, and how he learned to control that power over time.
One key event could be Naruto's lonely childhood. Growing up without parents, constantly being shunned by the villagers. Madara might see how Naruto coped with that, like when he sat alone on the swing. Another could be his encounter with Iruka, who was the first to really recognize Naruto as a person, not just the container of the Nine - Tails. This moment might be significant as it was a turning point in Naruto's self - acceptance.
Madara may view Naruto as a symbol of hope in a different way. He might realize that Naruto's past, full of hardships, has shaped him into a force for good. His experiences of loneliness and then finding friendship could make Madara see that Naruto has the potential to change the ninja world in a positive way. So, instead of just seeing him as a threat to his plans, he could start to see him as an ally or at least a worthy opponent with noble intentions.
Probably his time at the Ninja Academy. Naruto was always getting into trouble there, but it was also where he made some of his first friends. Also, his encounters with the Third Hokage could be shown. The Third Hokage was like a grandfather figure to Naruto, and their interactions were important in Naruto's development.
In a Naruto fanfiction where he has Madara's attitude, he could become more power - hungry. Madara was always seeking power to reshape the world according to his ideals. Naruto might start to view the tailed beasts not as friends but as tools for greater power. He could try to gather more chakra and perhaps even attempt to unlock new forms of power that are more in line with Madara's dark and ambitious nature, which would shock his comrades and enemies alike.
Well, in such a fanfiction, it might start with Naruto being in a situation where he becomes Madara's pet. Maybe at first, Naruto is defiant but as time passes, he could start to understand Madara's motives in some strange way. Madara, on the other hand, might initially see Naruto as just a possession but gradually develop a sense of attachment. It could be a really strange and complex relationship that unfolds as the story progresses.
One key event could be Naruto's time at the Ninja Academy. He was often alone and had no one to practice with, yet he still persevered. Boruto would see how Naruto's determination started early. Another event might be when Naruto fought against Haku and Zabuza. It was a dangerous battle that showed Naruto's courage. And of course, Naruto's training with Jiraiya would be important. Jiraiya taught Naruto so much, and Boruto would understand how this mentorship shaped Naruto into the person he became.
In this fanfiction, Naruto's character development could be seen as a counterpoint to Madara's. Naruto is all about hope, friendship, and protecting the village. Madara has been through a lot of pain and betrayal which led him to a path of destruction. If Naruto is like Madara in this fanfiction, his development might involve a struggle between his own beliefs and the allure of Madara - like power and ruthlessness. However, Naruto would probably still find a way to use any new - found power in a more benevolent way compared to Madara.
Madara could be experimenting on Naruto to understand the concept of the 'will of fire' that Naruto embodies. Madara has his own views on power and the ninja world, and Naruto's unwavering belief in the will of fire might be something he wants to dissect. He may think that by understanding what makes Naruto so strong in terms of his beliefs, he can either break that strength or use it to manipulate others. Also, Naruto is seen as a symbol of hope in the ninja world, and Madara might want to turn that symbol into something that represents his own ideals through these experiments.
In some fanfictions, it could be through a divine intervention by Kami. Maybe Kami sees Naruto's pure heart and his need for more power to protect the village. So, Kami decides to bestow upon Naruto the power of Madara's Sharingan as a way to give him an edge in battles against powerful foes.
In some fanfictions, it could be through a strange and powerful jutsu transfer. Maybe Madara, on the verge of defeat, decides to transfer his Rinnegan power to Naruto for some unforeseen reason, like seeing a new path for the ninja world in Naruto.
Madara could also save Naruto by using his knowledge of the ninja world. Maybe he has some inside information about a plot against Naruto and he intervenes in time to stop it. He might have discovered a secret plan by an enemy group and takes action to keep Naruto out of harm's way. This could involve manipulating events behind the scenes or directly confronting the threat.