Some secret organizations that have been manipulating bloodline abilities for their own gain could also be the antagonists. They would not want Naruto to disrupt their plans. They might send their most powerful agents to stop Naruto, leading to intense battles in the fanfic.
The hidden enemies within Konoha who oppose Naruto's ideas of peace and unity could be antagonists. They might spread false rumors about Naruto, turning the villagers against him. This growing animosity between Naruto and the village could result in him lashing out at Konoha, making those who spread the rumors antagonists in the fanfic.
Madara Uchiha could also be a possible antagonist in this scenario. Even if he is dead in the original story, in a fanfiction, his lingering influence or a resurrected form could manipulate Naruto. Madara was always against Konoha's ideals to some extent and might use Naruto as a tool to destroy what he hated.
A possible plot might involve Naruto being exposed to some ancient and powerful knowledge or artifact. This discovery gives him the means to 'destroy' bloodlines in the sense that he can change the very nature of chakra within a person. He might use this new - found ability to break the cycle of bloodline - based power hierarchies. He could start with the major clans like the Uchiha and Hyuga, and as he spreads his influence, the concept of bloodline superiority slowly crumbles, leading to a new era in the Naruto world where a person's worth is determined by their own efforts and skills rather than their bloodline.
There could also be some ancient monsters or spirits that are tied to Olympus' existence. They might rise up to defend it because their own survival is linked to the continued existence of Olympus. These could be powerful beings that Percy has never faced before, adding an extra layer of danger to his quest to destroy Olympus.
Well, it could start with Naruto seeing the dark side of bloodline powers being misused. So he decides to take matters into his own hands and develop a method to destroy bloodlines. This could lead to a huge rift in the ninja community, with some supporting him for trying to create equality and others opposing him because they value their unique family abilities.
Sasuke might be able to stop Naruto. They have a long - standing relationship and Sasuke has always been Naruto's equal in terms of power. He could use his Sharingan to try and break whatever is controlling Naruto or just fight him head - on and appeal to their old friendship.
Maybe it could be other ninja clans who are jealous of Naruto's newfound sword bloodline. They might see it as a threat to their own power and status in the ninja world.
The main antagonists could be members of an ancient clan who see Naruto's emerging powers from his bloodline as a threat to their own plans for power. They might fear that his newfound abilities will disrupt the balance of power they have been carefully cultivating for generations.
There are countless Naruto fanfictions out there. For a 'Naruto destroys bloodline fanfic', it might involve Naruto challenging the traditional view of bloodlines in the Naruto universe. Maybe he discovers a way to nullify the advantages of certain bloodlines through his own unique abilities or some new form of jutsu he creates. However, without a more in - depth search on the major fanfic platforms, it's hard to give a definite example. You could start by looking at the most popular Naruto fanfics on these platforms and then dig deeper into their descriptions to see if they match what you're looking for.
It could be an organization similar to the Akatsuki, but with a different goal. Instead of collecting tailed beasts, they are focused on conquering villages. Their army would be made up of powerful and diverse fighters, and Naruto would have to face their leader, who has some sort of special power or ability that makes them a formidable foe.