Who might be the main antagonist in a 'rwby ruby turns evil fanfiction'?

Perhaps it could be an evil version of one of Ruby's own relatives. Like an alternate version of her father or mother who has been corrupted by some dark force. They would then raise Ruby with their evil values, making her believe that what they do is right and leading her down a dark path.

The main antagonist could also be a new character created specifically for the fanfic. This character could be an ancient evil that has been waiting for an opportunity to corrupt a powerful Huntress like Ruby. They would then use Ruby's newfound evil nature to further their own dark plans, and Weiss, Blake, and Yang would have to face both Ruby and this new threat.

Well, one possibility is that Ruby could be influenced by a powerful and evil relic. Maybe she discovers a dark side of the relic's power and becomes corrupted by it, gradually turning evil as she starts to value power over her friends and the greater good.

It could be Salem. She has always been interested in the power of the silver eyes, and Ruby having those eyes makes her a prime target. Salem might send her minions to kidnap Ruby, which would lead to her disappearance.

It could be Adam Taurus. He's a well - known and very radical member of the White Fang in the RWBY universe. His extreme views and violent methods would put him directly at odds with Ruby's more peaceful and inclusive approach.

Dumbledore could be the main antagonist. Harry might see Dumbledore as having used him all along for some grand plan. If Harry turns evil, he would want to break free from Dumbledore's influence. Dumbledore, with his power and wisdom, would then try to stop Harry from causing too much harm, thus becoming the main opposing force.

It could be the Green Goblin. He might manipulate Spider Man in some way, perhaps by tricking him into believing that the only way to protect the city is to rule it with an iron fist. This would slowly corrupt Spider Man's good intentions.

It could be a powerful Grimm - like being that has evolved beyond the normal Grimm. This antagonist might have the ability to think and strategize like a human, making it a much more dangerous foe for Ruby and her team. It could be leading the Grimm attacks in a more organized way, targeting specific areas to cause maximum chaos.

It could be Yuno. Normally they are friends, but if Asta turns evil, Yuno might be the one to oppose him. Yuno has his own strong magic and a sense of justice that would make him a natural adversary.

There's a possibility that a new character could emerge as the main antagonist. Ruby's time - traveling could disrupt the normal flow of events, and this might create a new power - hungry or revenge - seeking character. This new antagonist could be someone who blames Ruby for the changes in the timeline and wants to stop her at all costs.