Avengers: Endgame (spoilers)

This is where Doctor Doom would make a lot more sense as the next big bad for the MCU than Galactus would. Galactus would pretty much be Thanos 2.0 as far as the stakes go. Doom can get at the Avengers on a much more personal level. They've even laid the groundwork for some of it.

They can build up Doom as the guy filling Stark's void. He survived the Snap and, in the five years between then and Endgame, was acquiring power and becoming an unseen rival to Stark Industries. Give him ties to Sokovia (either use it as a Latveria substitute or make it a neighboring country; either way would give him access to any leftover Ultron tech) and you've got a built in grudge against the Avengers. They can even play up his sorcery abilities to tie him to Doctor Strange and make him both a magical and technological threat.
He comes across as an ally first, filling in the void left by Stark to supply gear to the Avengers. Rhody, for one, probably can't go very long without Tony designing and maintaining suits for him. Same with Spider-Man. Hell, maybe Doom becomes an Avenger for a spell, or a consultant of sorts.
Of course, Doom has built trojan horses and viruses and whatnot into any of the tech they buy from him and he eventually turns on them. Maybe rip off the "Tower of Babel" storyline from Justice League, where he finds and exploits all of their weaknesses to pick them off one by one.
Do it right, and they don't even need to introduce the Fantastic Four at all.

 

That would be an excellent use of Dr. Doom, who could be a villain across multiple stories. Perhaps focus on his use of technology and when he seems beaten, then the sorcery becomes a factor.

 

They'd also be able to build some relationships between a lot of the characters. Rhody and Spider-Man, like I pointed out, would come into his orbit. He could be a rival to Strange, but not an enemy. Same with T'Challa, since Latveria would be an Eastern European version of Wakanda. Now that Vision is out of the picture, Doom could move in on Wanda and woo her -- with his eye on betraying her, of course.
This thing is writing itself.

 

Doom actually married Wanda in the comics at one point, or came close. I know they were a couple after she lost her memory for a period.

 

That was in the miniseries Avengers: The Children's Crusade. She had lost her memory after the whole destroying the Avengers, creating an entirely new reality with Magneto in charge and finally wiping out mutants thing. I don't think they actually got married. They were engaged, but the Avengers showed up on their wedding day and things went to shit from there.

 

Other than Doom and Galactus, who would be a worthy successor to Thanos as the big bad in the next phase of the MCU?

 

They could go the Thunderbolts/Masters of Evil route. Create another super team that becomes more popular than the Avengers, but it turns out they are actually villains.

They could even bring back Zemo, build on what he established with the ability to manipulate the public and the Avengers in Civil War. Zemo is a very different character in the comics, but he was actually the one to initially form the Thunderbolts.

They could also go with the Skrulls for something like the Secret Invasion storyline or perhaps even an Avengers vs. X-Men thing.

 

If they can get the deal worked out with Sony to use him, Norman Osborne.

 

I wouldn't hate having them follow something along the lines of what was done in the comics, with one movie adapting Secret Invasion with the Skrulls and the follow-up being a Dark Avengers thing with Osborne as the big bad.

 

NERDS!

 

Proudly.

 

That's the best thing about the proliferation of comic book movies. The nerds took over and the cool kids didn't even realize it.