The final candidate is the one who I hope and think it will be. That is none other than Namor The Sub-Marnier. On numerous occasions, the prince of Atlantis has come into conflict with the Black Panther and his native country Wakanda. One famous incident occurred when Namor, possessing the Phoenix Force, summoned a tidal wave to Wakanda that killed a bunch of civilians and nearly destroyed the city.
As one of the oldest characters in Marvel Comics history (created in 1939), Namor has a long and complicated history. The son of a human sea captain and an Atlantean princess, he has been both a villain and a hero. He possesses many abilities including, flight, super strength, endurance, and being able to breathe underwater. Physically he is more than capable of taking on T’Challa
One thing that Namor has that Doctor Doom doesn’t is he’s been teased before in the MCU. First in Iron Man 2, when a global map showing different locations had one of its spots in the middle of the Atlantic. Many think this is an indication of Atlantis. Also, during a scene in Avengers: Endgame, Okoye says that Wakanda scanners had detected an earthquake at the bottom of the ocean but didn’t think it’s any kind of issue. And if you believe a recent rumor that Atlantis will be featured in the upcoming Eternals film, then there are more teases on the way.
There are many stories you could tell with him. Perhaps Namor starts out as the villain, but later teams up with the Black Panther to take on a bigger threat. Maybe someone like Attuma a known Namor foe overthrows him. In turn, he turns to the Black Panther for reclaiming his throne.
Namor really does make the most sense. He would bring a good story, hype and he’s already been teased. MCU fans would absolutely love to see Namor. There have been so many fan-made pictures of actors who they want to play him. He undoubtedly should be the big bad.