Well, one way could be through some kind of strange jutsu gone wrong. Maybe Naruto was experimenting with a new type of chakra manipulation and it accidentally combined with some sort of mutagenic energy, similar to what created the Hulk. And then, poof! He starts turning into the Hulk whenever he gets angry. Another possibility is that he encounters a villain who has the power to transform others and decides to use Naruto as his guinea pig to create a super - strong and uncontrollable Naruto - Hulk hybrid.
Perhaps there's a crossover between the Naruto world and the Marvel universe at some interdimensional rift. Naruto, being the curious and brave ninja he is, investigates this rift. As he steps through, his body gets infused with gamma radiation (the same that created the Hulk in the Marvel universe). His body, not used to this foreign energy, starts to mutate in a similar way to Bruce Banner's, causing him to transform into the Hulk - like being whenever his emotions run high.
Well, in fanfiction, anything is possible. Maybe Naruto gets transported to the Sekirei world through some sort of magic or a strange portal. This could be the start of his journey to become a Sekirei. It could also be due to a curse or a wish gone wrong that transforms him into a Sekirei - like form.
Well, in a fanfiction scenario, Naruto could become Kazekage if there was some sort of political alliance between Konoha and Suna. Maybe after years of working together on various missions and sharing resources, the two villages decided to have a more unified leadership. Naruto, being a well - known and respected ninja, could be chosen to lead Suna as Kazekage. He has shown his ability to understand and work with different people, which would be crucial in leading a village not his own.
If Naruto loses all his friends in a tragic way, perhaps in a battle against an overwhelming enemy that the village could have prevented. His grief could turn into hatred towards the shinobi system. He may decide that the existing order is what causes all this pain and destruction, and then he starts to work against it, becoming a villain in the eyes of the village.
In a Naruto - becomes - a - Yonko fanfiction, Naruto's unique abilities would set him apart. For example, his Sage Mode gives him enhanced strength, speed, and perception. In the pirate world, this would make him a formidable opponent. He could also learn Haki, the power in the One Piece universe. Combining his ninja skills with Haki, he could easily take on other pirates and claim territories, eventually becoming a Yonko.
In a Naruto becomes a Terminator fanfiction, it could start with some sort of time - travel or interdimensional rift. Maybe a jutsu gone wrong sends Naruto to a world where the Terminator technology exists. Then, Naruto, with his ninja skills and strong will, might adapt to the new environment. He could use his chakra in unique ways combined with the advanced weaponry of the Terminator world.
Imagine a situation where the Akatsuki has a new member who has the ability to show illusions of other powerful beings from different universes. This new member shows Naruto the story of Thanos. Naruto, seeing Thanos' determination and his ability to amass so much power single - handedly, could get influenced. He might start to think that there are things he can learn from Thanos about achieving one's goals, no matter how extreme, and thus become a fan.
Another possibility is that Naruto's will and his existing skills attract the attention of a dragon spirit. Naruto is known for his determination and his ability to master difficult techniques. A dragon spirit, seeing his potential, could choose to merge with him or guide him on the path to becoming a Dragon Sage. This might involve him undergoing a series of trials, like facing his inner demons and proving his worthiness to wield the dragon - sage power.
One way Naruto could become a sniper in a crossover fanfiction is through some kind of magical or technological device. Maybe he discovers a weapon from another world that gives him sniper - like abilities. Another possibility is that he is trained by a character from a different universe who is an expert sniper.
One possibility in this fanfiction scenario is that Naruto is seeking a new form of power to protect his village. He somehow makes a deal with a demon or entity related to the Ghost Rider. This entity sees Naruto's strong will and determination and decides to bestow upon him the powers of the Ghost Rider. Naruto's existing abilities like his Rasengan could be infused with the Ghost Rider's powers, creating a whole new and unique attack. His ability to move at high speeds as a ninja would also be enhanced by the Ghost Rider's superhuman strength and agility.
Well, in a fanfiction, it might be due to a curse. There could be a curse placed on Naruto that slowly transforms him into Kushina Uzumaki. This curse could be related to some dark secret in the Uzumaki clan's past. Or perhaps a strange experiment by Orochimaru or another rogue ninja that goes wrong and causes Naruto to take on Kushina's form and some of her abilities.