An old rival of T'Challa's from his training days could be the main antagonist. This person was always jealous of T'Challa's status as heir to the throne and the future Black Panther. Now, he has found a way to enhance his own abilities and wants to prove that he is the better warrior by taking down T'Challa and claiming the Black Panther mantle for himself. He would know T'Challa's fighting style well, making him a very challenging opponent.
A group of Wakandan nobles who oppose Shuri's rule as Black Panther could be the main antagonists. They believe that the Black Panther should be a more traditional figure and that Shuri's focus on innovation and change is a threat to their long - held power and status. They might plot to undermine her at every turn, from spreading false rumors within Wakanda to allying with external forces against her.
It could be a rogue Wakandan scientist who is jealous of the daughter's unique abilities. He might see her as a threat to his own plans of taking over Wakanda's technology and using it for his own evil purposes. So, he tries to undermine her at every turn and stop her from fulfilling her destiny in Wakanda.
It could be another summoner who is jealous of the panther summoner's power. This antagonist summons a powerful and dangerous beast, like a giant snake, to constantly challenge the panther summoner and try to steal their power or reputation.
It could be someone who wants to steal the knowledge Naruto gained from the Black Panther. Maybe a rogue ninja or a power - hungry villain from another land.
It could be a villain who is after Beast Boy's powers. Since Beast Boy is getting trained by Black Panther and becoming stronger, this villain might see him as a threat. Maybe it's someone like Deathstroke who wants to stop Beast Boy from reaching his full potential under Black Panther's tutelage.
T'Challa is the main character as he is the Black Panther. His father also plays an important role in the origin story.
A good main villain could be a rogue Wakandan scientist who was once part of the research team but was cast out due to unethical experiments. This scientist, filled with revenge, could create a new weapon that targets Wakanda's most precious resource or technology. They could team up with some outside forces who are also interested in Wakanda's downfall, creating a complex web of threats for the heroes to deal with.
It could be a power - hungry Slytherin who doesn't like that Regulus is showing an interest in Gryffindor values. This Slytherin might see it as a betrayal to their house and try to stop Regulus by any means necessary, even if it means using dark magic.
Maybe the Akatsuki as a whole. They are a group of powerful and dangerous ninjas. The Black Knight's presence might disrupt their plans to collect all the tailed beasts. They would see him as an obstacle and try to eliminate him. For example, Pain might think the Black Knight is a threat to his vision of peace through pain and send his subordinates to fight him.
A new character could be the main antagonist. For example, a powerful alien who has heard of Goku Black's reputation and wants to prove himself by defeating the reincarnated warrior. This alien could have unique powers that are a challenge for Goku Black to overcome, like the ability to nullify ki attacks.