C Virus Leon Fanfic: Who could be the main antagonist?

Perhaps a story where Leon is the only one immune to the C virus and he is being hunted by those who want to use his immunity for their own evil purposes. He has to constantly be on the run while also trying to find a way to destroy the virus once and for all.

Perhaps a group of anti - technology extremists could be the main antagonists in an Ultron fanfic. They see Ultron as the symbol of all that is wrong with technology and are determined to take him down, no matter the cost. They might use their own advanced, but more rudimentary, technology to fight against Ultron. This would create an interesting contrast between Ultron's high - tech abilities and their more basic, yet effective, methods.

The main antagonists could be the same organizations they have always fought against. For example, Umbrella Corporation or any other bio - terrorist groups. These groups might see Ada's pregnancy as a weakness and try to use it against them. They could target Ada to get to Leon or try to harm the unborn child to stop Leon from interfering with their evil plans.

A powerful vampire could be the main antagonist. Vampires and werewolves are often enemies in such fictional settings. This vampire could be after Akakuro's pack's territory or have a personal vendetta against Akakuro himself.

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 possible main antagonist could be Eris, the goddess of strife. She might be jealous of Aphrodite's beauty and power and see Percy as a tool to disrupt Aphrodite's plans. Eris could send her minions to create chaos and conflict between Percy and Aphrodite, trying to make them turn against each other.

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.

Frieza could be a great antagonist. He has a history with Broly and would be interested in Bulma's technology. He might see Broly's new alliance with Bulma as a threat and try to break it up. Frieza could also want to use Bulma to create powerful weapons or devices for his own evil purposes.

The Queen of Hearts could be the main antagonist. She is known for her tyrannical rule in Wonderland. Her desire for absolute control could put her at odds with Batman, who is used to fighting against those who abuse power in Gotham. She might see Batman as a threat to her reign and try to eliminate him.