If Naruto absorbs Kaguya in a fanfic, it might lead to a very different storyline. He could use Kaguya's power to bring about a new era of peace more quickly. For example, he might be able to use her power to stop all forms of aggression instantly. Also, his appearance might change slightly, taking on some of Kaguya's physical traits. And his understanding of the chakra and the world's origin could be greatly enhanced.
Well, in a fanfic where Naruto absorbs Kaguya, it's a really interesting concept. Naruto is already extremely powerful, but with Kaguya's power, he could become a sort of god - like figure. He may be able to access the different dimensions that Kaguya could control with ease. His friends and allies would probably view him with a mix of awe and fear. His newfound power could also attract new enemies who are jealous or afraid of his strength. It could also lead to Naruto having to deal with the dark side of Kaguya's power that he may not fully understand at first.
One possibility is that Naruto's chakra nature could change completely. Since Kaguya had unique chakra, Naruto might develop new jutsu that are a blend of his own and Kaguya's abilities. For example, his Rasengan could gain the power to not only attack but also to heal, as Kaguya had some form of life - giving power. Also, his connection to the tailed beasts could be enhanced in unexpected ways, allowing for better communication and cooperation with them.
If Naruto absorbs the Juubi in fanfic, it could change the whole Naruto universe in that story. He may have new forms or abilities. Maybe he could use the Juubi's power to bring peace to the ninja world more quickly. He could also face new challenges as other characters might fear his new - found power.
If Kaguya is sealed in Naruto in a fanfic, Naruto could potentially use Kaguya's power for good. He might be able to access new jutsu or abilities that were previously unknown. However, there would also be risks. The power could be corrupting, like it was for Madara when he got some of Kaguya's power. Naruto would have to rely on his strong will and the support of his friends to keep from being consumed by it. He could also try to study Kaguya's power to find a way to break the cycle of hatred that has been plaguing the ninja world for so long.
Well, in such a fanfic, Naruto might gain some extremely powerful and unique abilities. Kaguya being his trainer could mean he'd learn ancient and forbidden jutsus. Maybe he'd also gain a deeper understanding of the chakra and the origin of the ninja world.
Well, one possibility is that Naruto could use his newfound power of absorbing Kaguya along with the time travel ability to prevent some of the major tragedies in the Naruto universe. For example, he might stop the Uchiha massacre, which would change the entire course of the story. It could also lead to a different relationship between Sasuke and Naruto, as Sasuke's motivation for revenge would be gone.
In some fanfictions, if Naruto absorbs the Shinju, he might gain an incredible boost in power. He could potentially have access to vast amounts of chakra, far beyond what he already has. This new power might allow him to easily defeat his enemies, even those who were previously much stronger than him.
If Naruto absorbs Broly in fanfiction, it could lead to some really interesting character developments. Naruto has always been about hard work and friendship, but with Broly's power, he might face new internal struggles. For example, he could struggle with the newfound brute force that might be at odds with his ninja way. Also, his friends might be a bit wary of him at first due to this sudden and extreme power change. But in the end, Naruto would probably find a way to use it for good, just like he always does.
Well, if Naruto absorbs Mizuki in fanfiction, it could be really interesting. Naruto is already quite powerful, but with Mizuki's essence added to him, his power level could skyrocket. He might be able to access new forms of chakra or have enhanced physical abilities. Also, it could create a whole new dynamic in his relationships. His friends might be a bit wary of this new Naruto at first, but then come to accept him as he still has his core self intact.
Well, if Naruto absorbs the shinigami in fanfiction, it's a really wild concept. He could end up with some really strange and powerful abilities. Maybe he could use the shinigami's power to bring back the dead, or he could use it to create some kind of super - jutsu that involves the manipulation of life and death. It could also change his personality, as the power of the shinigami might be a corrupting influence.
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.