Well, in certain fanfiction stories, Naruto realizes that he has to depend solely on his inner strength. So, he delves deep into his own chakra reserves and tries to understand and control it better. He could also study old scrolls by himself, learning forgotten techniques and using his own determination and willpower to adapt them to his fighting style, which gradually makes him stronger on his own.
Saitama's strength in the manga comes from his intense training and unwavering determination. He pushed himself to the limit every day, which eventually led to his overwhelming power.
Overall, the ending of Invincible comics ties up loose ends and leaves a lasting impression. It has a mix of action, drama, and emotional moments that bring the story to a satisfying close.
The ending of the Invincible comic is quite intense and unexpected. The hero faces a final showdown with a powerful adversary, and there are some major plot twists along the way.