It could be one of the Career tributes. They are often strong and ruthless in the Hunger Games, and would see Red Arrow as a threat.
In a Wiress Hunger Games fanfic, a Capitol official who has a personal vendetta against Wiress could be an antagonist. Maybe Wiress uncovered some of their secrets during her time in the Capitol, and now they are out to get her, using the Hunger Games as the perfect opportunity to get rid of her.
One interesting aspect could be how Red Arrow is integrated into the Hunger Games universe. Maybe he uses his archery skills to survive in the arena. Another aspect could be the new relationships he forms with the other tributes.
The main antagonist could be President Snow. He is always trying to maintain his control over the districts and the Hunger Games. If Peggy Sue is trying to change the system or help the tributes, Snow would be against her every step of the way.
In 'The Hunger Games', the antagonist is President Snow. His actions and decisions are at the core of the story's tension and opposition. He is determined to keep the districts in subjugation and will do whatever it takes to maintain his rule.
A young, brave pilot from a small, rebel - affiliated starship could be a main character. He's got great flying skills and uses them to his advantage in the arena. For instance, if there are flying obstacles or challenges, he can navigate through them easily.
It could be a young girl from District 11 who has been training in secret to be a fighter. She has a strong will to survive and wants to use her skills to bring honor to her district.
Perhaps an older man who has been through many hardships in his district. He volunteers for the games to protect his family and uses his life experience and wisdom to outwit the other tributes. He could be a very different kind of main character compared to the typical young tributes in the original story.
A person who has been ostracized in District 10 because they have a different view on how to handle the livestock. This character could be the main character in the fanfic as they enter the Hunger Games with a chip on their shoulder. They want to prove that they are not just a simple farmer or livestock keeper, but someone with great skills and intelligence that can survive and even win the Games.
A girl from District 12 could be a great main character. She could be different from Katniss, maybe she's more of a strategist than a hunter. She uses her wits to form alliances and outsmart her opponents in the arena.
Obviously Naruto himself could be a main character. He has the skills and the charisma. Sasuke could also be a main character. His brooding nature and powerful ninja abilities would make him a force to be reckoned with in the Hunger Games arena. Sakura, with her medical ninjutsu and growing combat skills, could also be a key character.