Originally Posted by
Endus
It should be Doom.
They've shown that the heroes of Earth can stand up to the best of the universe. So what about the villains of Earth? Seems a reasonable next step. Going with Galactus seems like a step up from Thanos + Infinity Gauntlet, but it's really a step down, and retreading the same kind of ground.
And hell, the MCU made frickin' Vulture a scary-ass villain. I think they can handle Doom. Just a few points;
1> Don't do a major redesign. Use the bolt-face mask and hood. You can tweak that, SLIGHTLY, to make it work, but it should be as recognizable as Spidey's or Iron Man's suits were. Also, no taking the mask off, not until the final fight, and probably not even then. It shouldn't matter who he is under the mask. He's Doom.
2> Doom wins. Doom wins basically every fight. The next major arc should be a lot of "heroes versus villain of the week", where said villain is working for Doom, and they beat the villain, but Doom gets what he wanted and gets away. At best, he loses, and then takes it back in a future outing. The whole sequence of 10+ films should be Doom coming out on top, and he should be even more present than Thanos. More like Loki.
3> Doom's reasonable. He can cut his losses. His motivation is sensible. He can take his case to the UN, against the heroes and SHIELD, and make his case, without lying or hiding anything, and win that vote, legitimately. I don't know what that plot is, maybe it's an improvement on Stark's "we need to protect the Earth", with an added "and Doom is the only one who can" rider.
He should be Stark without the compassion, Mysterio without the dishonesty, the Captain America of Eastern-European Pragmatism rather than American-made Freedom. The biggest strengths of the main heroes, without their moral and ethical hesitations to hold him back, and the intelligence to pull it all off.