MCU's Phase 4 needs the Red Guardian to unravel Natasha Romanoff's past and depict the US-USSR Cold War rivalry
MCU's Phase 1 introduced Russian flavor into the mix with Natasha Romanoff aka Black Widow (Scarlett Johansson) and Mickey Rourke's Ivan Vanko in 'Iron Man 2'. While one was a secret spy allied with the Americans, the other was the son of a genius bent on exacting revenge on Tony Stark aka Iron Man (Robert Downey Jr).
The next phase saw the Winter Soldier take his place in the MCU and encounter another Russian element. Bucky Barnes, the HYDRA-brainwashed supersoldier, played by Sebastian Stan, was experimented on at a covert HYDRA facility in Russia and turned into an enhanced assassin. He was responsible for the deaths of Howard Stark and Maria Stark.
It's easy to see all these Russian elements make valuable additions to these plotlines. Phases 1 and 2 also saw a lot of superheroes based outside the Earth and introducing the Russian element meant they had a formidable foe to fight against. Phase 3 was the lone exception as it never really saw new additions since the focus went to filling up the Avengers roster.
'Black Widow' is the first movie in Phase 4 and while it traces the origins of the Russian superspy, it will also take a leaf out of Phases 1 and 2 by introducing a character called the Red Guardian (set to be played by David Harbour).
The Red Guardian mantle has been taken up by multiple people in the comics but from the movie's perspective, the Red in focus is Alexi Shostakov. The character was introduced in Avengers #43 in August 1967. Shoskatov's history is rather tragic as he was orphaned during WWII and rescued by a Soviet officer, Vasily Karpov.
Karpov was later involved in the Winter Soldier program. Coming back to Shoskatov, he started off as a pilot in the Soviet Union and was one of the most decorated airforce men. Eventually, his skillset saw him getting picked for secret missions.
While the Red Guardian was not necessarily one of the most important characters, he was Russia's version of Captain America. They even stuck to the blueprint that was used to create the star-spangled superhero, sans the super serum.
It also makes sense to bring a Russian hero into the mix as he plays an integral role in Romanoff's life. 'Black Widow' is probably the last connection to the OG Avengers and it is important that the character's arc is completely rounded off. This means presenting characters who have played their part in making Romanoff who she is.
The other factor is the relation between the US and the Soviet Union. The movies in Phases 1 and 2 reflected the rivalry between the two countries that had its influence on pop-culture and trickled down to the movie plots as well. 'Black Widow' is probably the last movie we may see that has ties to Russia, and topping it off by introducing a storyline with the Red Guardian could be the perfect way to go.
'Black Widow' will hit theatres on May 1, 2020.