Who could be the main antagonist in 'naruto x female werewolf lemon fanfiction'?

It could be someone who also wants the power of the mask. Maybe a rogue ninja who has been researching the mask for a long time and sees Naruto as an obstacle to obtaining it.

Perhaps an ancient evil spirit that was sealed away long ago in Naruto's world but gets awakened by Ruby Lemon's presence. This spirit has the ability to possess people and use their skills for its own ends. It starts to cause chaos in the ninja villages and targets Ruby Lemon and Naruto specifically, seeing them as the key to either its complete destruction or its total domination.

It could be someone from a different ninja village who hears about the special jewelry that Naruto has. They send out their best agents, and Lemon could be working for them secretly. So, in this case, the main antagonist would be the leader of that ninja village who wants the jewelry at any cost, and Lemon is just a tool in their plan.

It could be a powerful vampire lord who sees the hybrid as an abomination and wants to destroy them. This vampire lord might view the mixing of werewolf and vampire blood as a threat to the purity of the vampire race.

It could be an evil ninja who wants to capture the female wolf for her unique powers. Maybe he plans to use her chakra to create a powerful weapon or perform a dark jutsu.

It could be a rogue ninja who has a vendetta against Naruto and sees Sister Lemon as an easy target to get to Naruto. This ninja might have some special powers that make him a formidable foe, like the ability to control shadows in a more sinister way than Naruto's shadow clone jutsu.

Maybe a powerful warlord who rules over the region where the winter lemons grow. He sees Naruto as a threat to his control over the valuable lemon resources and decides to eliminate him. The warlord might have an army of minions and some dark magic of his own that he uses against Naruto and his friends.

One option could be Kaguya from the Naruto universe. Her god - like powers would pose a great threat to Bayonetta. She could be trying to expand her influence into Bayonetta's world, seeing it as a new place to conquer.

It could be a dark wizard who wants to capture the nymph for her powers. He sees the nymph's connection to nature and wants to use it to gain ultimate power in the Naruto world.

It could be a rogue ninja who has also discovered a way to harness the power of Amaterasu in a corrupt way. This ninja might want to use the power to take over the ninja villages and Naruto stands in his way.