In a fanfiction scenario where Naruto kills Hanzo the Salamander, it could be due to Naruto's newfound power. Maybe he has mastered a powerful jutsu that gives him the upper hand. For example, if he has a super - charged Rasengan that can break through Hanzo's defenses. Another possibility is that Naruto has allies who help him set up a perfect trap for Hanzo. He could be strategizing with Shikamaru, who comes up with an elaborate plan to outwit Hanzo.
One consequence could be a shift in the power balance in the ninja world. If Naruto kills Hanzo, the village that Hanzo was protecting or ruling might be thrown into chaos. His death could also lead to his followers seeking revenge against Naruto or his village.
A plot twist might involve Hanzo being resurrected in a different form. Instead of being the feared Salamander Hanzo, he could come back as a more benevolent figure. He might then team up with Naruto to face a greater threat that is endangering the ninja world. They would have to overcome their past differences and combine their skills to succeed.
Their encounter could be different if Naruto was more powerful from the start. He could approach Hanzo with more confidence and instead of a battle of strength, it could turn into a battle of wits. Naruto might try to convince Hanzo to join forces against a common enemy rather than fight him.
One challenge is getting their personalities right. Naruto is very energetic and optimistic while Hanzo is more stoic and experienced. Balancing these two different personalities in the story can be tricky.
Another possibility is a complete character distortion in the fanfiction. The writer might decide to create a 'bad Naruto' version where he has lost all his positive traits. However, this is quite far - fetched considering the strong foundation of Naruto's character in the original series. It would be a very different and probably controversial take on the Naruto - Hinata relationship.
In a Naruto kills Thanos fanfiction, Naruto's sealing techniques could play a major role. He could use sealing jutsu to seal away Thanos' powers or even Thanos himself. Naruto has experience in dealing with powerful foes and sealing them away. Also, Naruto has the ability to sense danger and react quickly. Thanos, on the other hand, may underestimate Naruto at first. By the time he realizes Naruto's true strength, it could be too late for him.
In fanfiction, Naruto might kill a god through the power of his strong will and the unique abilities he has. For example, his Sage Mode could be enhanced to a level that allows him to overpower a god - like entity. Also, his Nine - Tails chakra could be combined with some new, made - up powers in the fanfiction world to give him the strength needed.
Well, in a fanfiction scenario, Naruto might kill Aizen if he manages to use his shadow clones to outwit Aizen's illusions. Naruto could also use his Sage Mode to sense Aizen's reiatsu and counter his attacks. Maybe he combines his Rasengan with some new jutsu he's developed specifically to deal with Aizen's powers.
Well, it could happen if Naruto has some sort of special weapon. For example, he might get a sword that can disrupt Hidan's connection with his voodoo - like powers. Once that connection is broken, Naruto could easily defeat and kill Hidan. Also, Naruto's growth in chakra control and strength could play a role. With his enhanced abilities, he could overpower Hidan and deliver a fatal blow.
Another possibility is that there is some sort of magical or otherworldly influence. Perhaps an evil force manipulates Naruto into believing that Drogo is a danger to his world or loved ones. So, Naruto, being the hero he is, takes it upon himself to eliminate the perceived threat. However, this would go against Naruto's usual nature of trying to understand his opponents first, so it would be an interesting twist in the fanfiction.