The Russos have explained what makes Doctor Doom a different kind of problem than Thanos: Thanos smashed his way through everything, and Doom plans.
The directors got into it with Fandango when asked about the Endgame Encore scene of Doom collecting Bruce Banner with what appears to be Latverian magic.
The interviewer also brought up the Latverian Witches seen at Comic-Con this year.

“Thanos Was Just A Brute Force Of Nature”
“Doom’s magic is an ancient magic,” the Russos explained. “He is a very powerful character, as you can see in the trailer, and he’s a genius.”
“He studies his foes. He understands them, and he’s also well planned. He’s not somebody who just does something off the cuff,” they continued.
“So everything is meticulous with him, and he knows that if he’s going to step on a battlefield against somebody, he has to have the tactical advantage or a power advantage against that person. So he’s very difficult to beat,” they added.
Then came the direct comparison.
“Thanos was just a brute force of nature. He would push his way through every problem,” they said. “Doom is much more Machiavellian and manipulative than Thanos in that regard.”

Robert Downey Jr. Playing Both Stark And Doom
Anthony Russo also addressed Downey playing the villain after a decade as Iron Man.
“Victor Von Doom is his own creation. He’s an original character, and he was fully approached that way by Joe and I and Robert,” he said.
“But it’s Robert Downey, and he played Iron Man, and he’s playing Doom, and there’s that connection. We’ll see where it goes from there,” he continued.
Joe Russo added, “It’s an interesting exploration between good and evil by having Robert play both Stark and Doom, and there’s a duality to explore there.”
The directors said they have always gone for villains “who have a layer of complexity to them, who have some validity to them.”
“You can’t create a character with Robert Downey without having a level of complexity to it. So Doom’s got that,” they said. “Happy to have him back.”
The same interview revealed the runtime comes in around two and a half hours, along with a tease about the ending and the Shang-Chi vs. Gambit fight.
Downey’s Doom arrives when Avengers: Doomsday hits theaters December 18.
