The penultimate episode of Marvel Studios' What If...? on Disney+ followed up on the cliffhanger debut of a new Ultron in the previous episode, which imagined a world where the robotic villain won. This led to a number of changes that saw Ultron inhabiting Vision's body while also gathering the Infinity Stones and incorporating them into his armor.
This dark reality in the multiverse created one of the Marvel Cinematic Universe's most powerful villains who could become a dangerous threat to the multiversal team of heroes that have been forming across the series. There are even a few powerful comic characters that What If...?'s Ultron would be able to defeat.
10 Thanos And The Avengers Were Both Taken Out By Ultron Before Even He Gained The Infinity Stones
Ultron's power levels were increased dramatically when he succeeded in transferring his consciousness into what would have been Vision in the main MCU reality. This saw him effectively take out most of the Avengers' heaviest hitters like Iron Man and Thor with only the power of the Mind Stone.
Ultron then surprised fans and Thanos when he sliced the Mad Titan in half and stole the Infinity Stones to further increase his power. Captain Marvel put up a good fight against Ultron in his new armored form, but even she fell to the galaxy-destroying power of the Infinity Stones when controlled by Ultron.
9 Ultron Has Already Beaten Adam Warlock Once
Adam Warlock is usually the go-to superhero in the Marvel Universe when the Infinity Stones are in play because he was bonded to the Soul Stone for so long. He helped the Avengers stop Thanos during The Infinity Gauntlet and played crucial roles in a number of Marvel comic events.
Ultron even faced Adam Warlock and the first roster of the modern Guardians of the Galaxy during Annihilation: Conquest, which saw Ultron expand his army with the alien Phalanx. Ultron was able to take over the body of Adam Warlock without the power of the Infinity Stones, so it's unlikely Marvel's cosmic hero would be able to stand up to What If...?'s overpowered version.
8 Genis-Vell Wouldn't Be Able To Stand Against Ultron
While Ultron was able to take out Carol Danvers/Captain Marvel, that isn't the only version of the powerful character that has appeared in the comics. Mar-Vell was the original hero who used Nega-Bands that granted him cosmic awareness, much like Ultron showed when he became aware of The Watcher.
The Nega-Bands were passed down to Mar-Vell's son Genis-Vell, who gained cosmic awareness that led to an increase in his abilities. After spending time as Captain Marvel, he became Photon and was able to manipulate cosmic energy, though it threatened his sanity and led to his death. If Photon were still alive in another reality, his weaknesses would make him susceptible to Ultron.
7 Ultron Would Annihilate Annihilus And His Annihilation Wave With The Infinity Stones
Marvel's cosmic universe was previously threatened by the powerful insectoid villain of the Fantastic Four, Annihilus, who launched an attack from his home dimension, the Negative Zone. His armada was known as the Annihilation Wave and destroyed a number of planets before Marvel's cosmic heroes were able to combine their forces and fight back.
What If...? showed Ultron making his own way through Marvel's cosmic universe much like Annihilus, though he had an army of Sub-Ultrons instead of an armada. While Annihilus wields the Cosmic Control Rod and would put up a good fight, Ultron and the Infinity Stones would be able to outpower Annihilus and end his Annihilation Wave.
6 Nova Is One Of The Universe's Strongest Guardians, But Ultron Is Stronger
Richard Rider/Nova has yet to be seen in the MCU, though in the comics he was the one responsible for stopping Annihilus during the Annihilation event. Nova has had varying power levels over the years as he has housed the entirety of the Nova Force, which is usually shared among an entire Corps of heroes.
While Nova has proven himself one of the most powerful members of the Guardians of the Galaxy, even the full power of the Nova Force would come up short in a battle against What If...?'s Ultron and his Infinity Stones.
5 The Fantastic Four Would Fall To Ultron Unless They Used The Ultimate Nullifier
The Fantastic Four are usually one of the first lines of defense when it comes to cosmic threats like What If...?'s Ultron, and Marvel's First Family has managed to persevere against impossible odds a number of times. Reed Richards has even worn the Infinity Gauntlet himself, with multiversal versions using it in their reality to sculpt and shape events for the better in most cases.
Yet it's very possible that the Fantastic Four would fall to the power of the Infinity Stone-powered Ultron and his unending armies of Sub-Ultrons given the feats he displayed in What If...? However, Reed Richards usually has an ace up his sleeve called the Ultimate Nullifier which can erase any being from the universe, along with whoever chooses to fire the powerful weapon.
4 Doctor Doom Would Try And Fail To Steal Ultron's Cosmic Power
One of the Fantastic Four's greatest enemies and occasional allies is Doctor Doom, the armored ruler of Latveria who has attempted to steal cosmic power a number of times over the years from characters like Silver Surfer, The Beyonder, and even The Watcher.
While it's very possible Doctor Doom would figure out a way to steal the incredible powers of What If...?'s Ultron, his track record proves that he's often his own worst enemy. Doctor Doom would likely get caught in a monologue and allow Ultron to reclaim his stolen abilities, giving the new multiversal threat the win.
3 Galactus And Silver Surfer's Power Cosmic Would Put Up A Good Fight Before Losing
The Marvel Universe is home to a number of cosmic beings like Galactus, who is better known as the World Devourer. Galactus uses the Power Cosmic to empower heralds like the Silver Surfer in order to find him suitable planets to consume and sate his eternal hunger.
Galactus is largely considered to be one of the strongest cosmic beings, with Silver Surfer standing tall against powerful characters like Thanos many times over the years. However, Ultron's control over the Infinity Stones and the power he exhibited during his battle with The Watcher puts him on an entirely different level that could take out Galactus and his heralds.
2 Hela May Be One Of Asgard's Most Powerful Gods, But Ultron Would Be Her Ragnarok
Thor and Loki learned about the existence of their powerful sister Hela, Goddess of Death, in 2017's Thor: Ragnarok. The MCU's Hela was an altered version of the comic character who shared similar power levels. After centuries trapped by her father Odin, she was unleashed back on Asgard and quickly took command after slaughtering hundreds of powerful Asgardian warriors.
Even Thor and his team of Revengers had trouble standing up to Hela and her deadly Necroswords. Thor was forced to unleash the Fire-Demon Surtur on Asgard to stop her by bringing about the prophesied Ragnarok. However, What If...? showed Ultron using his enhanced armies and power to take out Asgard faster even than Surtur, which would definitely give Hela a run for her money.
1 The Phoenix Force Would Probably Join Ultron As Its New Fiery Host
One of the most powerful forces in the Marvel Universe is the cosmic entity known as the Phoenix Force, which has possessed a number of hosts over the years including Jean Grey, Rachel Summers, the current host Echo, and even Wolverine in the far future.
The Phoenix Force has exhibited similar galaxy destroying abilities as Ultron displayed in What If...? which could make for an interesting matchup. However, since Ultron was able to transfer into Vision's living body which could act as a host, it's very likely that an encounter with the Phoenix would result in a partnership as both Ultron and the Phoenix live to destroy.