Content Warning: The following article contains spoilers for Doctor Strange in the Multiverse of Madness.
The Marvel Cinematic Universe continues Phase Four in an epic way through Doctor Strange in the Multiverse of Madness, which gives audiences a wild narrative that continues the stories of the fan-favorites Stephen Strange and the Scarlet Witch. It also introduces likable newcomers like America Chavez and alternate-reality versions of characters like Captain Marvel.
Some of the characters in the instant classic have shown that they're smarter than most in the Marvel movie, with admirable individuals like Earth-838's Christine Palmer and Doctor Strange himself proving that they can make the right decisions under pressure. The most intelligent among them often make choices that are for the greater good, but also almost always have a storied past in the MCU that proves how brilliant they can be.
Sinister Strange
As if the Carrie-esque scenes with the Scarlet Witch weren't creepy enough, fans meet the spine-chilling alternate-reality version of Doctor Strange, Sinister Strange. It's clear that he hasn't taken his own advice about the Darkhold exacting "a heavy toll," as it has clearly devastated his universe and himself during his attempts at finding a universe where he is happy with Christine.
If Sinister Strange was ever as reasonable and intelligent as Earth-616's Doctor Strange, there's no sign of it in his depiction in the Marvel movie. He has obviously become absorbed by his twisted reasoning and the Darkhold's part in it, going as far as killing other versions of himself and claiming he was doing those "Stephens a favor."
America Chavez
While it's amusing to hear America’s funny lines in Doctor Strange 2, there are also some frustrating moments that revolve around her inability to trust Doctor Strange. This is for a good reason, of course, as she has been betrayed by a variant of him shortly before their meeting, and she does eventually come around and sees that his Earth-616 version is different.
If America is intelligent, fans haven't quite seen that side of her in the MCU so far. She spends most of her time being afraid of the Scarlet Witch and even her own abilities, which again, are understandable considering her experiences. One scene that highlights her quick thinking happens during a crucial moment of the film where she says she "can't beat" the Scarlet Witch, so she gives her what she wants by forcing her to confront her horrific actions in front of Billy and Tommy. It's a decision that directly leads to the end of her rampage, and one that was only possible thanks to America.
Defender Strange
Despite only seeing him in action (and alive) during the opening sequence, it's obvious that Defender Strange is a strong variant. Wong mentions that it's nearly impossible to reach the Book of Vishanti, which means America and Defender Strange had to go through a lot to get to that point.
Defender Strange recognizes that one way to potentially save the multiverse is to betray America and take her powers for himself, which he believes is the only way out. Unlike Earth-616's Doctor Strange, he's unable to see the other less-deadly solution to the problem and ends up dying in the process. That said, it's still a smart plan for the greater good, but it just didn't work out the way he wanted it to.
Scarlet Witch
Every loss the Scarlet Witch has endured has contributed to her transformation into one of the MCU's most terrifying villains. Her mind is clouded by pain and rage, as well as the misguided knowledge from the Darkhold, which helps her believe that she can be with her kids somewhere else in the multiverse.
She's smart in the sense that she can strategically devise plans to go after America, just like how she uses a multiverse-hopping demon in an attempt to capture her. She is also able to identify others' weak points and use them to her advantage, like how she manipulates a fighter in Kamar-Taj. Of course, these are all done on the false and damaging belief that she can replace a version of herself out there and be Billy and Tommy's mother again. She's too narrow-minded and corrupted to be able to see how terrible her actions are, but she thankfully does one last smart thing by destroying every version of the Darkhold across the multiverse in the end.
Wong
Wong has become an increasingly significant character in the MCU, especially since taking his place as Sorcerer Supreme following Doctor Strange's disappearance. During Doctor Strange 2, viewers see that he has not wasted those years, as Kamar-Taj is full of dedicated and skilled fighters who are ready to defend the mystical city no matter the cost.
Since he has trained in the mystic arts for much longer than Doctor Strange has and even served as the librarian in Kamar-Taj, he's privy to some information that not even the most powerful sorcerers have access to. This is why the Scarlet Witch has to force information about the copy of the Darkhold out of him, as she knows that he's one of the few who would know about it. While his decisions in Multiverse of Madness don't carry the same weight as Doctor Strange's or the Illuminati, it's impossible to deny that he's among the smartest characters in the film.
Christine Palmer
Christine’s unexpected appearance in Earth-838 shocked a lot of fans, especially after it's revealed that she has a much different job there compared to her 616 counterpart. As a Multiversal researcher for the Baxter Foundation, Christine is responsible for "naming realities" and possibly designing the "amazing polycarbonate fishbowls" that successfully hold Doctor Strange and America in their research facility.
She also repurposes the "Sands of Nisanti" to develop the handcuffs that somehow prevent Doctor Strange and America from using their magical abilities. Beyond her scientific knowledge, Christine can also make the right choices under pressure, as she chooses to trust Earth-616's Stephen despite her experiences with her universe's variant of him. Viewers won't soon forget her instrumental role in the way Doctor Strange eventually controls the Souls of the Damned to reach Wundagore as well.
The Illuminati
Most of the best cameos in Doctor Strange 2 happen when the protagonist meets the members of the Illuminati – Mordo Supreme, Black Bolt, Captain Marvel, Captain Carter, Reed Richards, and Professor Charles Xavier. Together, they make up one of the most powerful groups in the multiverse, and it's no surprise that they don't have any trouble defeating the Titan Thanos as the Avengers did.
They make strategic decisions like portraying Earth-838's Doctor Strange as a hero for the public, while ensuring that their universe is safe from potential incursions via multiversal visitors like 616's Stephen and America. Their variant of Doctor Strange started the Illuminati so that there would be an authoritative body making the difficult choices, which includes murdering their own Stephen. Their multiverse-changing decisions haven't prepared them enough for the threat of the Scarlet Witch, though, but it's hard to blame them considering everything they have witnessed points to the fact that "the greatest danger to the Multiverse" is Doctor Strange. Plus, Charles Xavier's last-minute choice to trust Stephen should count for something.
Doctor Strange
Without a doubt, the smartest character in Multiverse of Madness is Earth-616's Doctor Strange. The Marvel movie made sure to emphasize that he's different from "other other" versions of him, who arguably wouldn't have been able to make the tough choice that eventually stopped the Scarlet Witch's murderous streak.
Doctor Strange has shown that he's intelligent from the moment he recognized that America is special to the point where he goes with Clea to correct his (or his variant's) mistakes. He anticipates and counters the Scarlet Witch's moves long enough to keep America alive, while making sure that he protects the people he loves like Wong and Christine in the process. Most importantly, Doctor Strange understands that he doesn't have to go down the same path as his variants did and knows that others like America and the Scarlet Witch can make the right decisions with a bit of trust and encouragement, too.