Namor McKenzie is also cited as being Marvel's first mutant. While this isn't true chronologically, he was definitely the first published Marvel hero who happens to be a mutant. Aligning himself with Norman Osborn during Dark Reign, Namor would seemingly choose the path of villainy as one of his Dark X-Men.
Alongside Emma Frost, they worked to undermine the actual X-Men, even going as far as to defeat Nate Grey, siphoning his power into new teammate, Omega. The topsy-turvy path of Namor's allegiance regarding his mutant heritage would only get weirder from there.
Defecting to the X-Men proper alongside Emma Frost, he stood with the almost extinct mutant populace. Namor would also be one of the five mutants granted Phoenix Force powers in Avengers Vs. X-Men, using it to attack the Avengers in the name of the X-Men.
PULLED IN ALL DIRECTIONS
Ultimately, Namor is a character with obligations to his people, genetic ties to marginalized mutants and friend to at least one person on each of Marvel's major super teams. His brash actions, short temper and formidable power make him as choppy as the seas he rules; but then, so are the pressures he faces.
He's not a pure Atlantean, so some denizens of the sea do not respect him, his mutant ties would see him away from Atlantis for too long and his friends often contribute to the factors that are a detriment to his oceanic empire. Perhaps it is not Namor's fault that he is a walking ball of conflict; it is all around him, and inside of him, too. But can such a character truly come to the MCU?
APPEARANCE IN THE MCU
The question remains as to when -- or indeed if -- Namor will make an appearance in the Marvel Cinematic Universe. If so, shouldn't it have been way back in Captain America: The First Avenger? It is reasonable to assume, however, that Cap's first MCU outing only showed a portion of World War II, and that the heroes could have met on several other occasions.
Of course, with so many superhumans around when Steve was thrust into the Avengers, he probably would have said something about Namor had he already known him. Then again, we did get to see the original Human Torch's costume in the film with no explanation, so maybe Namor exists there in the same vein. Or perhaps he's just a completely different kind of character.
Unfortunately, like Namor's past in the comics, his movie appearance is surrounded by uncertainty and potential contention. Kevin Feige has spoken about how Universal has the rights to Namor, and though Marvel seems to have reached a deal with them previously on Hulk, Namor is still a little tricky to pin down. So, although there was a reference to the Sub-Mariner in Iron Man II, his debut in the MCU is as uncertain as his allegiances.