Who could be the main antagonist in a 'mugetsu ichigo crossover fanfic'?

It could be Aizen from Bleach. Imagine if he somehow found a way to cross over into the Fairy Tail world. His devious and powerful nature would make him a formidable antagonist. He could manipulate the dark guilds in the Fairy Tail world to do his bidding and try to gain control over the powerful magic there, all while being a threat to Mugetsu Ichigo who he has his own history with in the Bleach universe.

One possible ally could be a powerful mage from a different anime in the crossover. This mage could help Ichigo understand the strange magic or energy in the new world he is stuck in. Also, Uryu might be an ally. His Quincy abilities could complement Ichigo's powers in Mugetsu form as they face new threats together.

A powerful dark wizard could be the main antagonist. This wizard could be from a third, unknown dimension and is seeking to harness the combined powers of Ichigo and fem Oga for his own malevolent purposes. He might have the ability to manipulate dark magic and create illusions to deceive our heroes.

Maybe a giant lemon - themed monster. This monster is created by some dark force that wants to disrupt the balance between the two worlds in the crossover. It has the ability to spit out acidic lemon juice that can corrode anything. Ichigo has to figure out its weakness and defeat it to restore peace. The monster could be controlled by an unseen force that is the real antagonist behind the scenes.

Well, perhaps in this fanfiction, Ichigo in Mugetsu form is stuck in a dimension where time and space work differently. He could start losing control of his Mugetsu powers and has to learn to master them again in this new environment. Along the way, he meets a character who has knowledge about his situation and helps him on his journey, which involves facing various challenges and foes.

Maybe in the fanfic, Mugetsu Ichigo teams up with some unexpected characters from another series. For example, he could meet characters who have unique abilities that complement his own, and together they face a powerful common enemy that neither could defeat alone. This would lead to some interesting character interactions and power combinations.

In a crossover with Snow White, the Evil Queen could be the main antagonist. She might be jealous of Tinkerbell's magic and try to capture her to use her pixie dust for her own dark purposes.

A plot could involve Mugetsu Ichigo losing his memories after a battle and ending up in the Fairy Tail world. He starts to learn about Fairy Tail magic and even develops some new skills by combining his existing powers with the magic there. Meanwhile, Fairy Tail wizards are trying to figure out who he is. When a powerful enemy emerges that is related to the Soul Reaper world, Ichigo's latent memories start to return, and he and the Fairy Tail gang must work together to defeat it.

There could be a group of corrupted Quincy who view Ichigo's resurrection as an abomination. They believe that his power goes against the natural order of things. So, they band together to try and eliminate him. They might have some new and dangerous weapons or techniques specifically designed to counter Ichigo's resurrected powers. This group could be led by a very powerful Quincy who has a personal vendetta against Ichigo or the Soul Reapers in general.

Madara Uchiha could be a great antagonist in this fanfic. Even though he was defeated in the original Naruto story, if he somehow gets resurrected and gets a chance to control the Juubi, he would be a formidable foe. He already had grand plans for the world in the original story, and with the Juubi's power, he could be even more dangerous. He might want to reshape the world according to his vision, and Naruto would have to fight him once again to protect everyone.