Naruto would likely be deeply hurt, not just physically but also emotionally. He has always idolized his mother, so an attack from her would be a huge blow to his psyche. His trust in family and those close to him could be severely damaged.
Definitely Sasuke. Their bond is such that Sasuke would not stand by and let Naruto destroy Konoha. He has his own reasons to protect the village now. Shikamaru is also a likely candidate. He's intelligent and would quickly figure out that Naruto's actions are wrong. He would use his strategic mind to try and stop Naruto. And Hinata, who loves Naruto deeply, would oppose him in the hopes of bringing him back to his senses.
He may also choose to defend himself without really fighting back. Naruto values Sakura as a friend and teammate, so he would be reluctant to harm her. He might just try to dodge her attacks and keep talking to her, hoping to snap her out of it.
In some fanfictions, it might be due to an alternate timeline or reality. A change in the past could lead to Kushina having different beliefs or loyalties. It could also be related to a new power or curse that affects her judgment and causes her to see Naruto as an enemy. However, this is often a very dark and dramatic turn in fanfiction stories.
It could be Orochimaru. He has always had his eyes on Konoha and might find a way to manipulate Naruto into attacking it. Maybe he uses some new experimental jutsu on Naruto to make him do his bidding.
Perhaps in the 'naruto attacks konoha fanfic', Naruto is being influenced by a new and powerful villain who has convinced him that Konoha's shinobi are corrupt. So, Naruto decides to take matters into his own hands and attacks the village to 'purify' it. It could also be that Naruto has some sort of misunderstanding about a decision made by the Konoha elders that he thinks is so wrong it warrants an attack on the village.
Obviously Naruto would be one of the main characters as the title implies he's the one attacking. And the Kages, like Gaara, Tsunade, and the other village leaders would also be main characters since they are at the summit that Naruto is attacking.
One idea could be that Naruto is under a powerful genjutsu that makes him see Konoha as an enemy. So, he attacks without realizing it's his home. Another could be that an evil entity has possessed Naruto, forcing him to turn against Konoha. It might also be that Naruto has been misled by false information about Konoha's dark secrets and decides to take action against it.
One good example could be a fanfic where Naruto has a panic attack during a high - stakes mission. Maybe he's faced with an opponent much stronger than he expected and the pressure causes the panic attack. Another could be in a situation where he's in a crowded place and memories of past traumas resurface, triggering it.