29 Brand New Characters Coming To MCU Phase 4
27. Alexei Shostakov/The Red Guardian - Black Widow
Along with her mother and sister, Black Widow's pre-Avengers family will be completed by her adoptive father, Alexei Shostakov. Played by Hellboy himself, David Harbour, Alexei will also enjoy the alter ego of the Red Guardian, essentially Russia's answer to Captain America.
When Natasha returns home, it would appear that it has been some time since the character has actually lived as the Red Guardian, as he is happy the suit still fits, even despite Melina telling him he's got fat. He doesn't seem to have missed a step however, as he looks to be handling himself when going toe to toe with Taskmaster.
Of all Natasha's family, Alexei certainly seems to be the happiest that they are all back together once again, however his history in the comics suggests a far more complicated role in the movie than just concerned father.
In the source material, Alexei was married to Natasha before the KGB faked his death to drive her further into the service of the Red Room. While this won't be the case in the MCU, the idea of deception and manipulation could certainly be adapted.