The main antagonist could be a dark - minded ninja who was once defeated by the previous wielder of the Suzumebachi. Now that Naruto has it, he sees it as a chance for revenge. He believes that by defeating Naruto and taking the Suzumebachi, he can restore his lost honor and also gain the power to dominate others. This antagonist would be constantly devising plans to outwit Naruto and get his hands on the powerful weapon.
It could be a powerful rogue ninja who wants the Suzumebachi for himself. He sees Naruto as a threat because he has the weapon and decides to target Naruto to get it.
In the 'naruto wields suzumebachi fanfic', the plot could revolve around Naruto finding the Suzumebachi during one of his adventures. Since the Suzumebachi is likely a very powerful and unique weapon, Naruto would need to train hard to control it. He may face challenges from other ninja who are envious of his new weapon. Naruto, being Naruto, would use the Suzumebachi not just for fighting but also to protect his friends and the village. He could develop new techniques that are a fusion of his own chakra - based powers and the abilities of the Suzumebachi, making him a one - of - a - kind ninja in the Naruto universe.
Another possibility is a new character created specifically for the fanfic. This antagonist could be a dark - chakra user who believes that the Samaheada's power should be used to reshape the ninja world according to his own twisted vision. He would view Naruto as a threat not only because he wields the Samaheada but also because of Naruto's reputation for bringing hope and change to the village.
The Organization in the Claymore world could be the main antagonist. They already have a lot of secrets and do some morally ambiguous things. If Naruto shows up and starts changing the status quo, like teaching Claymore warriors to be more independent, the Organization might see him as a threat and try to eliminate him.
It could be a rogue ninja who was once a student of Orochimaru and has now developed his own dangerous jutsu. He wants to take over the ninja world and believes the old ways are holding everyone back.
Orochimaru could be a great antagonist. He might want to use Shenron's power for his own dark experiments. He could try to steal the dragon balls and manipulate the wishes to gain immortality or create an army of powerful, immortal ninja.
It could be someone who opposes Naruto's newfound admiration for Ganondorf. Maybe a traditionalist ninja who thinks Naruto is straying from the true ninja path by getting influenced by Ganondorf.
Lex Luthor could be a great antagonist. He's always looking for power and knowledge. If he discovers Naruto's abilities, he might try to use them for his own gain or see Naruto as a threat to his plans in Smallville.
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.