WARNING: The following contains spoilers for What If...? Season 1, Episode 8, "What If... Ultron Won,?" streaming now on Disney+.
Part of the fun of superhero comics, power comparisons haven enjoyed a place in the Marvel Cinematic Universe, and in the minds of fans. Thor’s consternation at not being the “strongest Avenger” is one of Ragnarok's stand-out moments of humor, and the Hulk's inability to outfight Thanos at the beginning of Avengers: Infinity War gave a clear indication the Mad Titan couldn’t simply be beaten into submission. With the introduction of the multiverse and the imminent arrival of the Eternals, the MCU is moving into cosmic-level powers, which has resulted in some intriguing comparisons.
What If…?, in particular, has skewed the curve in terms of comparative power levels. In the process, the Disney+ series has suggested some figures who would be capable of killing Thanos, even when he's in possession of the Infinity Gauntlet. And while the Ultron-Vision hybrid in “What If… Ultron Won?” proved more than a match for Thanos, he wasn’t the only figure in that episode who may have been capable of defeating him him. Uatu the Watcher proved a surprisingly powerful match.
According to the Marvel comics, the Watchers -- among the oldest races in the universe -- swore an oath to observes events as they unfold, but never interfere. In the distant past, they attempted to aid a less-developed species, only to inadvertently cause their destruction. From that moment, they embraced non-interference. What If…? opens every episode with narration by Uatu (voiced by Jeffrey Wright), assuring viewers that as terrible as that week’s reality might be, he cannot take any steps to change what happens.
Choosing not to exercise one’s power isn’t the same as lacking it, however. And while “Ultron Won” makes a great deal of drama over what happens when power isn’t used, the Watcher is still a cosmic being of staggering abilities. That becomes apparent when Ultron (Ross Marquand) becomes aware of the Watcher's presence, and breaches the walls of his universe to begin the conquest of other realities. Yet, faced with the power of a genocidal AI in the Vision’s body and with the reality-changing abilities of the Infinity Stones themselves, the Watch not only withstands the robot’s attack, but pushes back.
That implies, indirectly at least, the Watcher could conceivably defeat Thanos as easily. “Ultron Won” depicts the Titan’s arrival on Earth in search of the final Infinity Stone, only for Ultron to slice him in half with the Mind Stone before the Mad Titan can so much as open his mouth. Thanos, thus, surrenders all of the Infinity Stones to Ultron, instantly creating an existential threat to the multiverse. If the Watcher could withstand such power, and even fight back against it, chances are he could also put Thanos, and most of his variants, in their place.
As the episode implies, it’s Uatu’s inability to act, rather than any limit to his cosmic power, that hampers him. Having sworn never to intervene, he’s slow to react in the face of an imminent threat. Ultron calls him on it as they fight, and the Watcher ultimately has to flee, presumably to assemble a team to tackle the menace. Again, however, that speaks more to his frame of mind than his raw power.
Such potential power bears out in the comics as well, most notably in Fantastic Four #50, in which Uatu provided the Ultimate Nullifier to save Earth from Galactus. Ultron-Vision may possess similar power levels, but the Watcher’s ultimate inability to defeat him stems more from will than lack of ability. More importantly, What If…? gives him the opportunity to weigh the consequences of noninterference, and confront the fact that his powers mean nothing if he won’t use them. That applies to Thanos as much as it does to Ultron.
To see Ultron's rise to power, Episode 8 of What If...? is streaming now on Disney+.