Well, obviously Percy Jackson and Jason are the main ones. Given that it's a bashing fanfic, they will be at the center of the story. Their actions, personalities, and relationships will be the focus.
Other characters from the Percy Jackson universe are also likely to be involved. Friends of Percy like Annabeth might be there to support Percy and show how he is better than Jason. Or characters associated with Jason could be present to either defend him (if the bashing is not one - sided) or to be used as examples of why he's not as great as Percy.
Another theme could be character flaws. It may explore the flaws of Jason more deeply than in the original works. Maybe it shows how his actions in certain situations, like his decision - making during battles, are not as good as Percy's. This can be used to create drama and conflict within the fanfic.
From the Tsukune side, Tsukune would be there as the character being bashed. His friends from his own story might also make an appearance, but mainly to be overshadowed by the Naruto characters. For example, Moka could be in it, but the focus would be on how Naruto characters are better in various aspects compared to her and Tsukune.
Naruto himself could be a main character as the fanfic might explore how his life could have been different without the Sandaime's influence. Another likely main character could be Orochimaru, especially if the fanfic focuses on the Sandaime's failure to deal with him properly.
Obviously, Percy Jackson himself would be the main character. The tigers that raise him would also be important characters. They could be like his family in the story.
Percy Jackson himself would obviously be a main character since it's a 'Reborn Percy Jackson Fanfiction'. His friends like Annabeth Chase are also likely to be main characters. She could play a crucial role in helping Percy adjust to his new life after being reborn. Grover would probably be there too, still being Percy's loyal friend. And the gods, especially those who have a connection to Percy like Poseidon, would also be important characters as they might have different reactions to Percy's rebirth.
Some of the likely characters could be the regular mortal kids at Percy's school. They might not understand his differences and bully him because of his ADHD and dyslexia. Another possibility is some jealous demigods who envy Percy's popularity or his special abilities.
In this fanfiction, Percy Jackson is the central figure as he controls the Styx. But other important characters could be Grover, his satyr friend. Grover has always been there for Percy and could provide support or comical relief. Also, Nico di Angelo could play a significant role. Given his connection to the underworld, he might have some insights or even a conflict with Percy regarding the control of the Styx.
Well, Percy Jackson himself would obviously be the main character. And since it's about being a slave of the gods, gods like Zeus, Poseidon, and Athena could be important characters as well, as they might be the ones either enslaving him or having some role in his enslavement or liberation.
Obviously, Percy Jackson and Kronos are the main characters. Percy is the hero, the son of Poseidon, with his powers over water and his ability to lead. Kronos is the powerful Titan, the main antagonist, with his devious plans to take over the world.
Percy Jackson himself would be the main character, obviously. Since he is the God of Matter in this fanfiction. His friends like Annabeth Chase would also likely be important characters. She could be there to support Percy and use her own intelligence to help him understand and control his new powers.