It could be a rogue ninja from within Konoha who has his own reasons for not wanting Naruto back. Maybe this ninja was jealous of Naruto's popularity and power before he left, and now fears that his return will put an end to his own plans for power within the village.
Perhaps an old enemy from Naruto's past, someone who was thought to be defeated but has now resurfaced. This antagonist might see Naruto's return as an opportunity to get revenge on him and on Konoha as a whole. They could have been biding their time, gathering strength, and now that Naruto is back, they start their malicious plot.
It could be a new villain who has been plotting against Konoha while Naruto was away.
It could be a rogue ninja from within Konoha who doesn't want Naruto to return because he fears Naruto's growing power will disrupt his own plans for power within the village.
The antagonist could be a new, self - proclaimed ninja god who wants to rule over all the villages. He sees Naruto as the only threat to his power, so he used a powerful spell to take away Naruto's godlike abilities. Konoha wants Naruto back to stop this tyrant. This antagonist might have an army of brainwashed ninja at his command.
A new character could be introduced as the main antagonist. Maybe a powerful ninja from another village who has infiltrated Konoha's politics. This character could be the one behind the idea of forcing Naruto back, with the intention of using Naruto as a pawn in a larger scheme against Konoha.
Perhaps an old enemy from Naruto's past that was thought to be defeated but has somehow returned stronger. Maybe Orochimaru, if he has found a new way to gain power and wants to test himself against Naruto once again. He might be jealous of Naruto's popularity and the fact that he was always seen as a hero, so he uses Edo Tensei to bring Naruto back just to defeat him and prove that he is the stronger one.
It could be a corrupt elder in Konoha. They might be power - hungry and see Naruto as a threat to their control. So they manipulate the situation to make Naruto the enemy.
Obviously, Naruto is the central character. But often, his friends like Sasuke, Sakura, and Kakashi are also involved. Sasuke might be there to have some sort of reunion or conflict with Naruto. Sakura could be the one to heal Naruto if he comes back injured. And Kakashi, as Naruto's former teacher, would be there to welcome him back or assess his new abilities.
It could be a rogue ninja from within Konoha who has embraced the 'darkness' fully and wants to reshape the village according to his own twisted ideals.
The main antagonist could be a new character. For example, a powerful ninja from a rival village who has a vendetta against Konoha. This ninja could manipulate Naruto into leaving Konoha by spreading false rumors about the village. Then, he tries to use Naruto's power as an assassin for his own evil plans.
It could be a long - lost relative of one of the old villains like Orochimaru. Maybe this person has been in hiding, training and growing in power, and now wants to take revenge on Konoha for what happened to their family member.