Maybe there's a corrupt elder in Iwa who doesn't trust outsiders. This elder sees Naruto as a threat to Iwa's traditional ways and tries to get rid of him. He might spread false rumors about Naruto within the village and try to turn the other ninjas against him.
It's possible that in Konoha, the ones who got Naruto banished in the first place don't want him to succeed in Iwa. They send spies to Iwa to cause trouble for Naruto and try to make it seem like he's still a threat to Konoha, which would put Naruto in a difficult position both in Iwa and in relation to his former home.
Well, one possibility could be that Naruto is banished from Konoha due to some false accusations. When he joins Iwa, he might start learning their unique jutsu and fighting styles. He could also face a lot of distrust at first from the Iwa ninjas because he's from Konoha. But as time passes, he proves himself and becomes an important part of Iwa, maybe even leading some missions against common enemies of both villages.
The main antagonists could be some of the conservative Iwa ninjas who oppose Naruto joining their village. They might see him as a threat to their traditional ways and values. Also, there could be some rogue ninjas from other villages who target Naruto because they see him as an easy target now that he's in a new and unfamiliar environment.
One possible plot development could be Naruto facing initial hostility in Iwa. Since he's from Konoha, the Iwa ninjas might be suspicious of him at first. But Naruto, with his determination and unique skills like the Rasengan, could gradually earn their respect. He might also learn new jutsu unique to Iwa and form new alliances, perhaps even finding a way to bridge the gap between Konoha and Iwa in the long run.
Maybe the main antagonist is the entire Iwa council. They might be the ones who order Naruto's abandonment because they fear his potential influence on Iwa. They would do everything in their power to keep him from uncovering their plans or causing unrest among the villagers.
It could be Danzo. He has always been a shadowy figure with his own agenda. He might see Naruto as a threat to his control over the village and engineer his banishment.
It could be a powerful Thalmor agent. The Thalmor are often seen as the bad guys in Skyrim, and if Naruto shows up, they might see him as a threat to their plans of domination. They could use their influence to get Naruto banished and then try to hunt him down.
The main antagonist could be a powerful Sith - like figure who has infiltrated the ninja world. This character might be manipulating events from the shadows, causing the village to suspect Naruto and leading to his banishment. They could have their own motives for wanting to take over the ninja world, like using its chakra for their own dark purposes.
Maybe the main antagonist is a group within Naruto's own village. The elders or some of the more conservative clans who banished Naruto in the first place. They fear that if Naruto returns as the banished emperor, he will change the power structure that they have been maintaining for so long. So they do everything they can to stop him from coming back, even if it means allying with outside forces.
A powerful Hollow could be the main antagonist. This Hollow could sense Naruto's unique energy and see him as a threat to its plans of taking over Karakura. It might constantly target Naruto and his new friends, trying to eliminate them one by one.
The main antagonist could be a power - hungry elder in Temari's own village. This elder might see Temari as a threat to their authority, especially if she has been getting too much influence or support from other ninja. So, they frame her for a crime that leads to her banishment.