In Marvel's Ultimate Universe, Iron Man's secret twin brother flipped Avengers: Endgame on its head as he wielded Mjolnir to break Captain America's shield and takedown Thor. However, much like Thanos' attack in the MCU, Gregory Stark was ultimately defeated. However, in this case, Stark suffered a brutal death like Thanos, as Thor killed him with a powerful strike of lightning. But Stark did serious damage before being stopped.
Marvel's Ultimate Universe takes place in an entirely different continuity than the main Earth-616 universe but still served as an important inspiration for the Marvel Cinematic Universe. The elements used include Iron Man's mentorship of Spider-Man, the Samuel L. Jackson-inspired Nick Fury, and SHIELD's role in forming the Avengers. The Ultimate Universe was the product of the creative minds of Brian Michael Bendis, Mark Millar, Mark Bagley, Joe Quesada, Bill Jemas, and Bryan Hitch and featured numerous highs and lows within the new world. One of the most insane moments was when Iron Man's twin brother Gregory Stark used Mjolnir to attack the Avengers, in a moment that flipped an iconic future Avengers: Endgame storyline on its head.
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In Ultimate Avengers vs. New Ultimates #6 by Mark Millar, Leinil Yu, Stephen Segovia, Terry Alanguilan, Jeff Huet, Jason Paz, Sunny Gho, and VC's Cory Petit, Iron Man's twin brother Gregory Stark takes over SHIELD and sells their superhuman secrets to escalate pro-democracy rebellions. As Marvel's Ultimates take on the Avengers in a massive, deadly battle, Stark arrives on the scene. Thor attempts to throw Mjolnir at the villain, but Stark catches it (thanks to his nanite powers) and uses it
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