Who could be the main antagonist in a 'luffy meets dragon fanfic'?

The World Government could be the main antagonist. They see both Luffy as a growing threat to their rule as a pirate and Dragon as a revolutionary. When Luffy and Dragon meet, the World Government might send their strongest agents like the Admirals to stop them from joining forces. The World Government's strict control over the world and their desire to maintain the status quo would put them in direct opposition to Luffy and Dragon.

The World Government could be the main antagonist in a more complex way. They could be secretly manipulating events to pit Dragon and Luffy against each other. For example, they could spread false rumors about Luffy being a tool of the revolutionaries, which would make other pirate crews and kingdoms target him, and at the same time make Dragon look bad for having a son who is causing so much chaos. This would force Dragon and Luffy to either fight each other or find a way to clear their names together.

A powerful new pirate group could be the main antagonist. They might be after the same treasure or territory as Luffy and Shanks. They could have some unique and dangerous abilities, like the ability to control sea monsters. Their leader could be a former crewmate of a well - known and feared pirate, who has his own vendetta against both Luffy and Shanks for some past reasons.

A powerful dragon - themed pirate could be the main antagonist. This pirate has a crew of dragon - like creatures and they are causing chaos across the seas. They have a grudge against Luffy for some reason, perhaps because Luffy has unknowingly entered their territory or stolen something valuable from them.

A time - traveling pirate who has his own agenda and wants to change the course of pirate history for his own gain could be the antagonist. This pirate might be jealous of Luffy's future achievements and try to stop him from ever becoming the Pirate King by changing things in the past.

Well, one possible plot could be that Luffy, while on one of his adventures, accidentally stumbles upon Dragon in a secret island. They initially don't recognize each other, but then some events unfold that make them realize their connection. Maybe they end up having to team up to fight against a common enemy that is threatening the freedom of the island's inhabitants.

It could be an evil shinobi who wants to disrupt the meeting between Naruto and Kushina. Maybe they know that Kushina has some special knowledge or power that she could pass on to Naruto, and they don't want that to happen.

Ra's al Ghul could also serve as the main antagonist. He might have a new plan for Gotham that involves using Catwoman as a pawn. He could be aware of her relationship with Batman and try to use it to his advantage. Batman would have to not only save Gotham but also rescue Catwoman from Ra's al Ghul's clutches.

It could be a rogue Sound ninja who has his own agenda. Maybe he wants to start a war between Konoha and the Sound Village to gain power in the chaos. He would see Naruto as a threat to his plans and try to eliminate him.

It could be a jealous artist named Max. Max has always been overshadowed by Bendy and Betsy's talent. So, he devises a plan to steal their ideas and take over the art world in their story. He starts spreading rumors about Bendy and Betsy to turn other artists against them.