In some fanfictions, Naruto's chakra - enhanced strength is shown as being able to shatter mountains. His punches, powered by chakra, can create shockwaves that level entire landscapes. This is often an exaggeration compared to the original series, but it makes for exciting reading.
In some fanfictions, there are basic levels where Naruto can enhance his normal strength just a bit for simple tasks like lifting heavy objects. Then there are intermediate levels where he can fight on par with mid - level villains. And at the highest level, his chakra - enhanced strength is god - like, able to reshape the world around him.
One way is through training with unique and powerful entities. For example, he might train with a long - lost sage who teaches him how to tap into deeper levels of his chakra. Another way is by inheriting new powers that boost his chakra. This could be from an ancient bloodline that gets awakened in the fanfiction.
His Rasengan would be stronger and more easily spammable. He could also use the Sage Mode more freely as he doesn't need to worry about chakra exhaustion. Maybe he could even combine different jutsus more often due to having an unlimited supply of chakra.
One possible reason could be that Naruto has access to some new and powerful jutsu. Maybe he discovers a secret family technique or is taught by a very powerful sage. This new knowledge gives him an edge over Kakashi.
One interesting concept could be a character unlocking the hidden potential of the chakra gates in a unique way. For example, they might discover a new sequence of opening the gates that gives them powers beyond what was thought possible in the original Naruto lore.
There are a few novels that I can recommend to you, in which the male protagonist obtains great power in different ways. First of all," Extraordinary Female Cultivator " was a cultivation novel in which the female protagonist was a surgeon. The male protagonist obtained super strength through possessing a mutated divine sense. Secondly, Ritual to the Heavens was a modern fantasy novel. The male protagonist wielded the Supreme Demon Sword, causing turmoil in the three worlds and finally obtaining great power. In addition," The Invincible Martial God " was also a novel in which the male protagonist embarked on the path of becoming a strong person by obtaining a supreme-grade spiritual meridian and finally became the Invincible Martial God. These novels all meet your requirements for the male protagonist's strength enhancement. I hope you will like these recommendations.
One consequence could be that he becomes extremely powerful. His physical abilities like strength, speed, and endurance are enhanced. He can also use more powerful jutsus with the extra chakra boost from the Kyuubi.
One interesting way is when Naruto absorbs chakra through his shadow clones. In some fanfictions, the clones can be used not just to gather information or attack, but also to absorb the chakra of the opponents they interact with. Then, they transfer this absorbed chakra back to Naruto, making him more powerful.
Perhaps there is an ancient artifact or a powerful curse that causes Naruto to absorb all chakra. In the fanfiction world, it's common to introduce such unique elements. For example, he might find a magical scroll that, when opened, starts sucking in all the chakra in the vicinity and then channels it into Naruto. Or it could be a curse placed on him by an enemy, but instead of harming him, it gives him this strange power to absorb all chakra.