Avengers: Doomsday will see a new “super-soldier brotherhood” forming that could finally plug the Steve Rogers-sized void in the Marvel Cinematic Universe. This comes via David Harbour, who reprises his role as Alexei Shostakov, the Red Guardian, in the upcoming Marvel Studios film. Speaking to Entertainment Tonight, Harbour discussed the bond forming between Alexei, Bucky Barnes, and John Walker.
“I’m building a sort of brotherhood with my boys, the Winter Soldier, and also with Wyatt Russell’s new Cap, and I like that bromance between the three of us,” Harbour said. “That sort of love triangle has been really fun to play as well.”
These three men represent different versions of the super soldier serum’s legacy in the Marvel Cinematic Universe. That formula that turned Steve Rogers into Captain America. Rogers’s friend and former fellow soldier, Bucky Barnes, was injected with a version of the super soldier serum as part of Hydra’s efforts to transform him into the killer called the Winter Soldier.
John Walker took another version of the Super Soldier serum of his own accord during his attempts to succeed Rogers and become the new Captain America. However, failing to live up to that mantle, Walker receded into the shadows in the less-public role of the U.S. Agent, taking orders from Valentina Allegra de Fontaine.
Alexei himself was meant to be the Soviet answer to Captain America, dosed with his country’s version of the Super Soldier serum. His physical abilities could rival those of Rogers, though his lifestyle and years in prison had somewhat reduced those abilities from their peak.
Ironically, the person who ultimately took on Captain America’s mantle is Sam Wilson, the former Falcon. He hasn’t ever taken any version of the super-soldier serum.
Steve Rogers Returns in Avengers: Doomsday, but his Super Soldier Legacy Lives on Without Him
Marvel Studios shocked MCU fans when it released a teaser trailer confirming that Steve Rogers will return in Avengers: Doomsday. It’s unclear what his role in the new film will entail. However, one thing that Harbour’s comments allude to is that the legacy of the super-soldier serum has been alive and well in the MCU even without Rogers.
While Bucky and John Walker clashed previously in The Falcon and the Winter Soldier on Disney+, the Thunderbolts* movie brought them together on the same side for the first time and introduced Alexei into the mix. That more than half of Marvel’s “New Avengers” team has taken the super soldier serum in some form speaks to the lasting power of Dr. Erskine’s work and the meaning that Rogers’ time as Captain America brought to it.
There’s More to Avengers: Doomsday Than Just Super Soldiers
Avengers: Doomsday is a movie with a lot going on, so it obviously won’t be all about this super soldier trio. Harbour acknowledged other aspects of the film as well, confirming that “Alexi and Yelena have, of course, a lot of beautiful stuff” in reference to the long-standing surrogate father relationship that Alexei has with Yelena Belova, another of his New Avengers teammates.
Harbour also said that the scale of the film dwarfs even the biggest project in his career thus far. “That movie is huge. I mean, I thought that Stranger Things 5 was big, but this is kind of the biggest thing I’ve ever done,” he said. He also teased Robert Downey, Jr.’s role in the film, saying, “I’m really excited for you to see what Downey’s doing. I think he’s really special.”
Avengers: Doomsday opens in theaters on December 16.
Release Date
December 18, 2026
Director
Anthony Russo, Joe Russo
Writers
Stephen McFeely, Michael Waldron, Jack Kirby, Stan Lee
Vanessa Kirby
Sue Storm / Invisible Woman
Joseph Quinn
Johnny Storm / Human Torch
Ebon Moss-Bachrach
Ben Grimm / The Thing