Maybe through some sort of ninja jutsu that allows Naruto to absorb the essence or power of others. It could be a new, experimental jutsu that he discovers or is taught specifically for this purpose.
Well, it could be that Naruto, as the son of Thanos, has some sort of conflict between his ninja values and the power - hungry nature he might inherit from Thanos. Maybe he has to struggle with not using the Infinity Stones in the wrong way, while still trying to protect his village from other threats. He might also face discrimination from his fellow ninjas who fear his Thanos - like abilities.
In this fanfiction plot, perhaps Thanos' actions in the Marvel universe start to affect Naruto's world. Naruto then sets out to find the source of the disturbance. When he encounters Thanos, he is initially outmatched. But as the story progresses, Naruto befriends some of the Marvel heroes who teach him about Thanos' powers. Naruto then trains hard, combines his ninja skills with new knowledge, and in a final epic battle, he manages to kill Thanos. The story could also include Naruto's internal struggle as he is in a completely different world with different rules and enemies.
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, if Naruto absorbs Thanos, he might gain incredible power. Naruto already has his own set of powerful jutsus, and by absorbing Thanos, he could potentially combine Thanos' strength, durability and perhaps his control over the Infinity Stones (if they exist in that fanfic's scenario). He could use this new - found power to protect his village in a whole new way, or even expand his influence to other realms or planets.
A possible plotline is that Thanos hears about the powerful chakra in the Naruto world and decides to conquer it. Naruto stands up to him, and during the fight, Naruto unlocks a new form of his power that is on par with Thanos' strength with the Infinity Stones. Along the way, Naruto teams up with some of his old foes who also realize the danger Thanos poses. They all fight together to protect their 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.
Well, if Naruto was raised by Thanos, it would be a very strange and interesting story. Naruto's personality of never giving up might clash with Thanos' cold and power - hungry nature. Naruto would probably try to influence Thanos in a positive way, perhaps make him see the value of life other than just power. He might also learn some unique combat skills from Thanos, which would make him an even more formidable ninja. However, it would be a constant struggle for Naruto to hold on to his own values while being under Thanos' influence.
Well, Naruto has his powerful jutsus like the Rasengan and Sage Mode. Thanos, on the other hand, is super strong and has the Infinity Stones. But in fanfiction, it could go either way. Maybe Naruto could use his shadow clones to overwhelm Thanos and then hit him with a super - powered Rasengan. However, Thanos could use the Infinity Stones to turn Naruto's attacks against him. It really depends on how the writer of the fanfiction wants to portray the battle.
He would probably be more power - hungry. Thanos was constantly seeking power through the Infinity Stones. Naruto, who has always been about protecting his village and friends, could shift his focus more towards personal power gain. This might lead him to isolate himself from his friends as he pursues greater power, just like how Thanos was mostly alone in his quest.