Sasuke would likely be a very tough opponent. He has his Sharingan and is extremely skilled in ninjutsu. His rivalry with Naruto also means he would be highly motivated in a fight.
Neji could also pose a significant challenge. With his Byakugan, he can see Naruto's every move and has the Gentle Fist technique, which can disrupt Naruto's chakra flow. He is a very strategic fighter.
It could be an enemy who has the power of sound. This opponent might be able to create sonic blasts with their music. Naruto would have to figure out how to counter these sound - based attacks, perhaps by using his wind - style jutsu to disrupt the sound waves.
In a Game of Thrones OC swordsman fanfiction, there are several contenders for the most formidable opponent. One could be the Mountain. His brute strength and combat experience would pose a great challenge. He's known for his brutality in battle and his large size gives him an advantage in close - quarters combat.
It could also be a sparring session gone wrong. Naruto might be training with the Konoha 12, but his new and powerful techniques are too intense. This causes the others to feel threatened and they end up in a full - on fight. Naruto would then have to control his power and show his friends that he doesn't mean to harm them.
I think some of the younger ninjas in the village would support Naruto. They look up to him as a role model. Also, those who have been helped by Naruto in the past, like the families of the villagers he saved. They would see that Naruto is fighting for what's right and would stand with him against the council. Additionally, some of the outcast ninjas who feel oppressed by the council's rules might also join Naruto.
Madara Uchiha, if he were to somehow be involved in the Battle City scenario. His power level is extremely high, and his experience in combat is far greater than Naruto's at the start. Naruto would have to really dig deep and use all his skills, plus any new ones he's developed, to stand a chance against Madara in Battle City.
Sakura and Sasuke would likely be his allies. They have been through a lot with Naruto and would stand by him. Also, some of his old friends from the Hidden Leaf like Shikamaru and Kiba might join in. They have always supported Naruto in the past and would do the same in this situation.
Naruto would probably win. He has the Nine - Tails' chakra which gives him a huge boost in power. He can also enter Sage Mode and has mastered many powerful techniques over the years. Zeref is strong, but Naruto has faced some really tough opponents and has always found a way to come out on top. In a fanfiction fight, Naruto's determination and willpower would also play a big role.
Some of the elders in the council are also very hated. They are usually portrayed as being old - fashioned and stubborn. They oppose any new ideas or changes that could potentially disrupt the status quo in Konoha. Their lack of understanding of the younger generation, like Naruto's generation, and their reluctance to adapt to new threats make them disliked in these fanfictions.
I think Gaara could be a really tough opponent for Naruto in an MMA - like scenario. Gaara has great control over his sand, which could be used defensively and offensively in a fight. He's also very resilient and has a lot of experience in combat. His stoic nature would make it difficult for Naruto to read his moves and find an opening. And Gaara's determination to win is on par with Naruto's.
If we consider a Naruto - Danzo fight in a fanfiction, Naruto has several factors in his favor. His training with Jiraiya and other experiences have made him a formidable ninja. He can go into Sage Mode, which enhances his physical abilities and gives him access to more powerful jutsu. Danzo, while being a shrewd and experienced ninja, has his weaknesses. His over - reliance on the Sharingan and his somewhat underhanded methods might not be enough against Naruto's raw power and unwavering spirit.