In this kind of fanfiction, Naruto might have used his new and powerful jutsu that he developed secretly. Maybe it was a super - enhanced Rasengan with some special chakra nature added to it, which was strong enough to overpower Orochimaru.
In some fanfictions, Naruto defeats Orochimaru by mastering a new and powerful jutsu. This jutsu could be something he discovers on his own during intense training, allowing him to overpower Orochimaru's snake - like techniques.
Well, in some fanfictions, Orochimaru might use some forbidden jutsu. He could have combined his knowledge of resurrection techniques with some unique chakra sources. Maybe he found a way to reverse the death process by using the power of the snakes he has a connection with. For example, he could have used the regenerative abilities of the snakes' chakra to bring Naruto back to life.
The Orochimaru character in "Naruto: I Am Hinata" was a woman, and Naruto was cursed by her. I recommend a novel for you. It's called "The Next Four Generations of Naruto Orochimaru". It tells the story of Orochimaru's rebirth as a new trend, dedicated to helping the leaves leave the rotten world. I hope you like this fairy's recommendation. Muah ~😗
One consequence could be a shift in the power balance among the ninja villages. Since Orochimaru was a powerful and feared figure, his death might cause some chaos as his former allies or subordinates try to either avenge him or claim his resources. For example, some of his secret labs and experiments might be up for grabs, leading to potential conflicts.
In some fanfics, Naruto might use his new and powerful jutsu that he has mastered over time. Maybe he combines his Sage Mode with the power of the Nine - Tails in a unique way that Orochimaru can't counter. For example, he could use the Nine - Tails' chakra to enhance the range and power of his Sage Mode attacks, and then catch Orochimaru off - guard.
One possible reason could be in the realm of artistic interpretation in the fanfiction. The author might want to explore a different aesthetic or a unique plot where Naruto has some physical or behavioral traits similar to Orochimaru for shock value or to create a new kind of character dynamic.
Since Orochimaru had many experiments and secrets, his death at Naruto's hands in the Chunin Exams fanfiction could lead to a scramble for his research. Other villages or even some rogue ninjas might try to steal his notes and facilities. In Konoha, Naruto might be pressured to reveal what he knew about Orochimaru's plans and secrets. This could put him in a difficult position as he may not know everything. Also, Sasuke, who had a connection with Orochimaru, might have a complex reaction. He could be angry at Naruto for killing Orochimaru, or he could see it as a sign of Naruto's strength and be motivated to become stronger himself.
In this fanfiction, their relationship could be full of tension. Orochimaru is a character who often pursues power through unorthodox means. Naruto, on the other hand, values life and friendship. So, they would constantly be at odds. But at the same time, there would be a sense of loyalty between them as brothers. Orochimaru might try to manipulate Naruto at times, while Naruto would be trying to redeem his brother, leading to a very tumultuous relationship.