If Naruto gains the power of Beerus in fanfiction, he would become extremely powerful. His already impressive combat skills combined with Beerus' god - like power would make him nearly unbeatable. He could easily defeat the toughest of foes in the Naruto universe with a single blow.
One interesting plot could be that Naruto discovers a hidden ancient jutsu during a solo mission in an uncharted land. This jutsu gives him the power to manipulate time on a small scale, like slowing down an enemy's attack. Another plot might involve Naruto making a pact with a powerful spirit that grants him enhanced strength and the ability to fly. There could also be a plot where Naruto is exposed to a strange energy source that unlocks a new form of chakra, which he then has to learn to control and use effectively against his enemies.
One of the most common allies in Naruto gains power fanfiction is Hinata. She has always been in love with Naruto, and when Naruto starts to gain power, she is right there by his side. She might use her Byakugan to help Naruto in battles or in his power - exploration. Another ally could be Shikamaru. His intelligence is a great asset, and he could help Naruto strategize how to use his new powers most effectively. Additionally, the Sage of Six Paths is often involved as an ally. He might appear to Naruto in visions or directly in person to guide him in his power - gaining journey, teaching him about the deeper secrets of chakra and the ninja world.
One great Percy gains power fanfiction is 'Percy's Ascent'. In it, Percy discovers an ancient power within himself through a series of trials. It's really exciting as it shows his growth from a normal demigod to a super - powered one. Another one is 'Power Surge Percy' which focuses on Percy getting a new kind of water - based power that no one has seen before.
One popular theme is self - discovery. As Percy gains power, he often has to figure out who he is now and how this new power fits into his identity. Another theme is the struggle for control. The new power can be overwhelming, like in 'Percy's Ascent' where he has to learn to control his newfound abilities to avoid hurting those he loves.
He might gain enhanced perception. This could allow him to see chakra flow more clearly, similar to how the Sharingan can. So in battles, he can anticipate his opponents' moves better.
Another way could be via some sort of magical artifact. For example, he discovers an ancient amulet that has the power to enhance his natural abilities. When he touches it, it starts to merge with his essence, gradually making him stronger and endowing him with new powers like the ability to control different elements related to water, not just manipulate it.
He might face internal struggles. Since it's the power of his enemies, it could have a corrupting influence. He has to constantly fight against the darker aspects of that power, like the urge to use it for revenge or in a more aggressive and unethical way.
He could also face challenges related to the knowledge required to use his power effectively. In fanfiction, there might be ancient texts or prophecies that he needs to decipher in order to fully understand and utilize his new powers. But these texts could be written in a long - lost language or be guarded by powerful entities, making it difficult for him to access the necessary information.
Madara Uchiha could also be an antagonist in this scenario. Even if he's dead in the original story, in the fanfiction, his influence or some sort of resurrection could occur. He might view Naruto's immortality as a hindrance to his own plans for the ninja world or simply be jealous of Naruto having such a power that he never had.