Well, the main antagonist could be the self - doubt within Hinata. Even though he meets the Little Giant, his own insecurities could act as an obstacle. He might doubt if he can live up to the Little Giant's example or if he's worthy of the advice he's getting. But through his interactions with the Little Giant and his own determination, he would have to fight against this internal antagonist to become a better player.
In this fanfiction, it's possible that the main antagonist could be an old rival of the Little Giant. This person might see Hinata as a threat because of his association with the Little Giant. They could try to create problems for Hinata during matches or training, like spreading false rumors or trying to psych him out. However, Hinata, with the inspiration from the Little Giant, would overcome these challenges.
Well, in this fanfiction, Hinata might learn some amazing volleyball techniques from the Little Giant. Maybe they'll have a friendly match and Hinata will gain more confidence in his skills.
Another possibility is that there is a group of anti - jinchuriki people who see Naruto as a threat because of his connection to the giant fox. They might try to kill Naruto to get rid of the 'giant fox problem'. Their leader could be the main antagonist, someone who has a deep - seated hatred for anything related to the tailed beasts.
It could be Neji. Even though they are family, Neji has been quite tough on Hinata in the past. His overbearing nature and the way he has sometimes looked down on Hinata could be the final straw that makes her snap.
Perhaps a jealous Hogwarts student who is envious of Harry's connection with the giant squid. This student could try to disrupt Harry's relationship with the squid, maybe by spreading false rumors about the squid being dangerous or by trying to harm the squid in secret. They might think that if they can get rid of the squid, they can get more attention or power within the school.
It could be a powerful warlock who has found a way to manipulate time and space. He wants to stop Paige and Prue from joining forces because he fears their combined power. So he creates various obstacles and illusions to keep them apart.
Maybe a powerful rogue ninja who has discovered a way to steal the powers of divine entities. He sets his sights on Amaterasu and Naruto because he knows that if he can combine their powers, he will be unstoppable. He creates various traps and illusions to separate them and weaken them so that he can carry out his evil plan.
A powerful new pirate group could be the main antagonist. They might be after the same treasure or territory as Luffy and Shanks. They could have some unique and dangerous abilities, like the ability to control sea monsters. Their leader could be a former crewmate of a well - known and feared pirate, who has his own vendetta against both Luffy and Shanks for some past reasons.
There could be an ancient force that is awakened by the meeting of Harry and Hela. This force wants to destroy both of them because their combined powers could potentially stop it from achieving its goal of spreading chaos and destruction throughout all the realms. It would use all kinds of devious means to try and separate them and defeat them one by one.
Maybe a powerful warlord from Negan's world who somehow follows him into Artemis' realm. This warlord, with his own thirst for power and destruction, would oppose both Negan (if he starts to side with Artemis) and Artemis herself, wanting to take over the new world he has found.
It could be another god who is jealous of Zeus' interest in Atreus. Maybe a god who feels that Atreus is an outsider and doesn't belong in their divine affairs.