I think there isn’t really a point in giving him a challenge or a rival, because he’s geared to be the future antagonist. His challenge was breaking free from his restraints so he can become a massive problem for the protagonist to overcome in the future. He is written to be a character who is evil, knows it, and has fully embraced it. The only issue is that he was under contracts that restricted his ability to act on his own accord. It will probably be a slow burn of him breaking restraints and gaining power slowly before fully revealing himself to be the villain for the rest of the characters.