Sasuke is often one of the characters. Given their complex relationship, Sasuke might see Naruto's banishment as another wrong done by the village and decide to support him in his revenge, especially if it means taking on the village's corrupt elements.
Another possible supporter could be Gaara. Gaara, having had his own experiences of being an outcast, might empathize with Naruto. He could provide Naruto with a place to stay during his banishment and offer his military might and resources to help Naruto seek revenge on those who wronged him in the village.
Sasuke could be one of the characters to support Naruto. Given their complex relationship and Sasuke's own issues with Konoha in the past, he might see Naruto's cause as just. Another one could be Jiraiya. If he were alive and found out about the real reasons behind Naruto's revenge, he might side with Naruto as he always cared for him deeply. Also, some of the outcast ninja within Konoha, like those who have been discriminated against because of their bloodline or lack of skills, might support Naruto as they also have grudges against the village system.
Betrayal is a very common theme. Often, a character is betrayed by someone they trusted, like a friend or a village, which then sets them on the path of revenge.
One interesting plotline could be Naruto being banished and then seeking revenge by training in secret with a powerful hermit. He might learn new jutsus and return to the village to expose the corruption that led to his banishment.
Definitely Iruka. He has seen Naruto grow up and has always supported him. Then there's Shikamaru. He's smart and he can see Naruto's value. He might support Naruto even if it goes against the village's decision at first. And of course, Kakashi. He has mentored Naruto and knows his potential, so he could be in Naruto's corner in these fanfictions.
One common theme is justice. Since Sakura is banished unjustly, she is seeking revenge which is often seen as a form of justice in these stories. Another theme is redemption. Sometimes, through her revenge journey, Sakura also redeems herself or others.
Power. In these fanfictions, Naruto often gains godlike powers, which is a central theme as he uses these powers for revenge. For example, he might have enhanced jutsu or new abilities that make him almost unbeatable.
One common theme is justice. Naruto seeking revenge is often seen as a way to right the wrongs done to him or his loved ones. It's about making the guilty pay for their actions.
One common theme is redemption. Naruto often uses pranks as a way to make those who have wronged him understand his pain, leading to a form of redemption for both sides. For example, he might prank a bully who used to pick on him, but in the end, they become friends.
Hinata could also be a common character. She may try to help Naruto secretly, or be heartbroken by his banishment and strive to change the village's decision. Another character could be Kakashi. He might be one of the few who believe in Naruto's innocence and try to find a way to bring him back to the village.
Naruto and Kurama are the central characters for sure. But there could be new characters created specifically for this fanfiction. For example, there might be a group of villains who were responsible for whatever event that triggered Naruto's need for revenge. They could be some sort of dark ninja clan or a secret organization that has been plotting against Naruto and the Hidden Leaf Village for a long time. And of course, Naruto's friends like Sakura and Kakashi could also be involved in the story, trying to either support or stop Naruto's revenge - driven actions.