Ultron Sigma

Ultron Sigma is the merged form of Ultron and Sigma that appears as an antagonist in Marvel vs. Capcom: Infinite. 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. As with previous Megaman X titles, Ultron Sigma also evolves into a final form in the final battle, known as Ultron Omega.

History
After Ultron and Thanos uses the Reality and Space to enter Capcom Universe's Abel City, Ultron uses the Reality Stone to hack the Abel City's barrier system and meets Sigma alone where the two villainous robot formed an alliance for same method besides betraying Thanos, elimination of all organic life. At Sigma's Lab where Sigma introduce the two Marvel villains his base, Sigma and Ultron initiates their plan to betray Thanos, with Sigma had Ultron to stab his body and uploading his mind to the latter's body, thus creating Ultron Sigma. After defeating Thanos and took the Space Stone, Ultron Sigma finally transformed "their" old Ultron form with both Space and Reality Stones, and begin to use the said two stones to converge both Marvel and Capcom world each timelines and realities into.

At some point after the Convergences on his 88 days of reign, Ultron Sigma already overthrown a merged city of Asgard known as Xgard (a fusion between Marvel's Asgard and Capcom's Abel City's Highway), and formed another alliance with Grandmaster Meio, entrusting him a Power Stone to develop an ultimate weapon powered by Sigma virus and Power Stone itself called Gravitron Core, using the core as a bomb to infect across the Earth when it falls successfully. Ultron Sigma also captured Zero and rewritten his core routine into Meio's brainwashed guards known as "Oblivion". 88 days, the heroes began to raid Xgard to restore the throne from Ultron Sigma. As Ultron Sigma comes out and taken out most of the heroes, Thor Odinson, alongside Rad Spencer, challenges Ultron Sigma for the throne of Xgard, with Ultron Sigma declaring arrogantly that their will is law and thus they will destroy them. Regardless of whether the player wins or loses, however, the first fight against Ultron Sigma will end the same way once Ultron Sigma's health is whittled down to a third: Ultron Sigma will disable Spencer and Thor with a chest blast and a beam saber slash, respectively, and then decries them as pitiful before asking if they even realize how powerless they truly were. He then steps on Thor's hand just as he reached for Mjolnir, and declared that he is not to weep for the Asgardians due to their achieving perfection under his rule. He then cruelly tells Thor that he'll soon "be their prince once more" before charging up an energy blast on his arm to transform him into a Xgardian. Before he could land the final blow, however, Ultron Sigma was shot in the back. Unphased by the gunshot, Ultron Sigma, realizing that Chris Redfield was behind him and shot him, calmly asks him if the commander had something to add in terms of great insight. Chris, however, merely tells him that he's going down. Ultron Sigma expresses some mock-disappointment in that all he had to offer was a "banal cliché" before declaring it to be fitting as final words from him. Ultron Sigma then levitates up and proceeds to charge up an attack above him before firing at Chris Redfield. However, Captain America deflects the blast with his shield, while Strider Hiryu retrieves Thor and teleports behind, with Ultron Sigma noticing just as it happens. The heroes then escape via Doctor Strange's portal, although Ultron Sigma nonetheless is glad over the overall turn of events despite losing his quarry.

He soon found that the heroes had been trying to distract Ultron Sigma for Chris and Doctor Strange's rescue ops to rescue Thanos. In case if Thanos hasn't been found by "themselves", it is revealed that Ultron Sigma had been implanting an immature Sigma virus into Thor's body before Chris and Doctor Strange's ops arrived in time after successfully rescue Thanos, and Thanos alerts the heroes that they are too late to prevent the Sigma virus matured in Thor's body, thus the heroes lost their renowned Thunder God of Norse now turned Ultron Sigma's most loyal puppet. As the heroes splits up under the tips from Thanos, Ultron Sigma had some of their Sigma-virus powered drones to trail Captain America and Chun-Li behind, as well as infecting Dah'ren Mohran to invade Valkanda (a merger nation between Marvel's Wakanda and Capcom's Val Habar) for Time Stone, which is currently under Black Panther's hand.