Ultron Omega is the final boss for Marvel vs. Capcom: Infinite, a further evolution of Ultron Sigma taken as a last resort to defeat the heroes. Similar to Ultron Sigma, he is voiced by Jim Meskimen and Chris Tergliafera, the voice actors for Ultron and Sigma, respectively. His "voice" is that of both Ultron and Sigma's voices overlapping each other, owing to his being fused from the two characters.
Ultron Omega has the top half strongly resembling Ultron's torso, albeit with a more powerful build, while the bottom half resembles Sigma's head, in particular the form of Sigma's head from the battle on the Final Weapon. He also had massive hands, which he can fire beams at his foes, or, in the case of Dante, entrap them in an energy field. Said hands appear to be the hands of "Gamma Sigma" from X5.
After Dante tricked Ultron Sigma into destroying himself by retrieving the Soul Stone, he transformed himself into this grotesque form, and then captured Dante before he could evade his limbs vowing to "return the favor." Ultron Omega then declared, alongside his new identity, that, being perfect, they cannot be destroyed. However, Spider-Man proceeded to intercept the Soul Stone with his webshot and sent it flying. Ultron Omega then ordered his servant, a corrupted Thor, to destroy the heroes. However, Thor, having caught the Soul Stone, was restored to his original self and refused, citing that he cannot have his soul and is not his puppet, despite earlier taking his will and strength before joining up with X. Thor then declared he will make sure Ultron Omega pays for the evil he had wrought upon the Asgardians. Ultron Omega, however, laughed off his claim, citing that they have transcended such "limited concepts" as Good and Evil. X then shoots back that they should "transcend" their joint attack. They then attacked him before wounding him to such a degree that they were forced to release Dante. Just as this is happening, a portal opened up with Doctor Strange, Ryu, Zero, Frank West, and Gamora emerging, with Iron Man attempting to announce he has a special delivery for Ultron Sigma, only to interrupt himself and note that the latter has "grown" upon realizing he's not actually Ultron Sigma anymore. He then asks X if he's ready before supplying him with the Infinity Buster via his blueprints and Doctor Strange lifting X up via his telekinesis, with X inserting the Power Gem. Ultron Omega then declares in irritation that the heroes have "interfered enough." Captain Marvel then tells everyone to cover X, realizing that this is their chance to destroy him. Ultron Omega then declares that they will soon feel "their" wrath and that they should kneel before the heroes' "god", only for Captain Marvel to shoot back that she's encountered a lot of gods, and claims that of the gods she encountered, Ultron Omega isn't even among her top 10. Ultron Omega then roars at her in rage, with Dante declaring that they should get the party started. Ultimately, after a harrowing fight, they managed to do significant enough damage to him for him to falter. At Iron Man's command, the heroes then supply X with the Time, Mind, and Soul Gems to power the Infinity Buster. Iron Man then, after marveling it, declares it to be called the Infinity Buster before promptly activating the weapon telling X to "let it rip." However, the sheer power of the cannon's charge was enough to have X undergo massive convultions due to having problems controlling it, even in his Ultimate Armor, resulting in Doctor Strange inquiring the heroes to lend him and Morrigan their strength so they can channel it into X so he can focus the Infinity Buster's power enough to end Ultron Omega for good. They do so, and X then manages to aim the buster after using a charged shot to end the menace, with Captain America confirming he had indeed been destroyed when X upon regaining consciousness inquiring of Ultron Omega's status.
- The theme song for the battle against Ultron Omega is a orchestra remix of Sigma's first phase battle theme from Mega Man X2 and, to a certain extent, his second phase battle theme in Mega Man X6.