Who could be the main antagonist in a 'naruto has a gunblade' fanfic?

One possible plot could be that Naruto discovers the gunblade in a hidden, ancient shinobi arsenal. He initially struggles to master it as it combines two very different combat elements - ranged shooting and melee slashing. However, with his determination, he gradually learns to use it effectively in battles against new, powerful enemies that are immune to his regular jutsu.

It could be a rogue ninja from a forgotten clan who is jealous of Naruto's new - found power from his hidden bloodline. This antagonist might try to steal Naruto's bloodline ability for himself.

Maybe the gunblade was created by a rogue ninja who had a fascination with both modern - day weapons and traditional ninja tools. Naruto gets his hands on it during a mission where he has to stop the rogue ninja from using it for evil purposes. As he uses it, he realizes it has special chakra - enhancing properties that he can use to his advantage in battle.

It could be Orochimaru. He's always been interested in unique powers and abilities. The idea of X - 23's mutant abilities and Naruto's jinchuriki powers would be very appealing to him. He might try to capture them both to use in his experiments to gain ultimate power.

A new character could be created as the antagonist. For example, an Uchiha who has been corrupted by the power of the Sharingan and wants to use Naruto's special Uchiha - related abilities for his own evil purposes. This character could be jealous of Naruto's unique position within the Uchiha - related story and try to take it from him.

It could be a rogue ninja who has mastered parkour to an extreme level. He uses his skills to steal important ninja artifacts and Naruto has to stop him. This antagonist would be very fast and agile, making it difficult for Naruto to catch him using normal ninja techniques.

Madara could still be the main antagonist even in a 'naruto bankai fanfic'. He senses Naruto's new power and realizes it could be a threat to his plans of world domination. He adapts his strategies and attacks Naruto with all his might, trying to prevent Naruto from fully mastering and using his Bankai - inspired power to its fullest potential.

A powerful and corrupt ninja from another village could be the main antagonist. He hears about the unique knives in Naruto's village and decides to steal them to increase his own power and the dominance of his village. He would stop at nothing to get his hands on these knives, even if it means starting a war between the villages.

A mysterious figure within Konoha who has a hidden agenda. This person doesn't like the idea of Naruto breaking the norms and wearing a dress. They secretly manipulate events to make Naruto's life difficult while he's in the dress. For example, they might arrange for Naruto to be in situations where his dress - wearing causes maximum embarrassment, all in an attempt to make him conform to the traditional ways.

It could be Orochimaru. He has always been interested in the power of the dead and bringing back the strong. He might have found a way to reanimate Naruto for his own evil purposes, like using Naruto's power to take over the ninja world.