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.
In fanfiction, there could be a magical or chakra - infused artifact that enables Naruto to absorb Thanos. For example, a special scroll or a unique weapon that has the power to draw in and assimilate other beings' powers. Naruto might find this artifact during one of his adventures and, after learning how to use it, use it to absorb Thanos.
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.
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.
In some fanfictions, Naruto might absorb Momoshiki through a unique kekkei genkai. For example, if the author creates a new form of chakra manipulation that allows Naruto to assimilate Momoshiki's power during their battle. This could be a result of Naruto's Uzumaki bloodline having some hidden potential that gets unlocked in the heat of the fight.
In some Naruto fanfictions, Naruto might absorb DNA through special jutsu or abilities. For example, he could have a unique kekkei genkai that allows him to take in and assimilate the genetic material of others. This could potentially give him new powers or abilities related to the DNA he absorbs, like if he absorbs the DNA of a Sharingan user, he might gain some form of Sharingan - like abilities.
In some Naruto fanfictions, Naruto might absorb animals through special jutsus or abilities. For example, he could have a unique kekkei genkai that allows him to take in the essence or chakra of animals. It could also be related to some sort of pact or bond he forms with the animals, which then enables him to absorb their powers.
In some fanfictions, it could be through a special jutsu. Maybe Naruto discovers a long - forgotten jutsu that allows him to merge with his dark counterpart. This jutsu might require a great deal of chakra control and concentration.
There are fanfictions where Naruto absorbs the bijuu during a life - threatening battle. As he is on the verge of defeat, he somehow taps into an unknown power within himself and ends up absorbing the bijuu to turn the tables. This often involves a strong emotional connection and a will to protect, which acts as a catalyst for this absorption.
In some fanfictions, Naruto might absorb chakra through unique jutsu. For example, he could have a new, self - created technique that allows him to draw in ambient chakra from nature more efficiently than in the original series. This could be a result of some special training he undergoes in the fan - created story.
Well, there are different ways it can happen in fanfiction. One way could be that Naruto and Mizuki are in a battle, and during the fight, Naruto accidentally activates a latent ability that allows him to absorb Mizuki. Maybe there is some sort of ancient seal on Naruto that reacts to Mizuki's presence and starts the absorption process. Another possibility is that Naruto is exposed to a strange chakra - infused object that was once connected to Mizuki, and this object triggers the absorption.
In some fanfictions, Naruto might absorb Chakra through a special jutsu. For instance, he could use a self - created jutsu that allows him to draw in Chakra from his surroundings or from other characters he's in contact with.