The Falcon and The Winter Soldier is another entry in the Marvel Cinematic Universe experiment as a living, evolving story. It's more than the sum of its parts, more than the individual movies or characters. And the most common trope in MCU stories is the hero having to fight an evil version of themselves.
In The Falcon and The Winter Soldier, Sam Wilson (Anthony Mackie) and Bucky Barnes (Sebastian Stan) have to fight multiple dark version of Captain America. Bucky himself was a dark version of Captain America in Captain America: The Winter Soldier. In the first Captain America, Steve Rogers (Chris Evans) fights the Red Skull (Hugo Weaving), who's basically Captain Nazi. In this show, Sam has to grapple with whether he should become the next Captain America and he has to face off against Karli Morganthau (Erin Kellyman), a chaotic Anarchist terrorist version of a super-soldier, and John Walker (Wyatt Russell), who becomes an evil version of Captain America. Sam even meets Isiah Bradley (Carl Lumbly), a hidden African-American super-soldier who's a tragic mirror image to Steve Rogers and And the show even gives us Baron Zemo (Daniel Bruhl) as a Greek chorus giving a running commentary about the themes of the story. The show is a veritable hall of mirrors of shadow doubles of Captain America.
Carl Jung in his writings on archetypes defined the "shadow double" as a dark reflection of a character and their traits. Superhero movies and especially the MCU have turned it into a common trope of the genre. The superhero often fights an evil version of themselves in order to prove their worth. In all 3 Iron Man movies, Tony Stark (Robert Downey, Jr.) has to fight evil versions of Iron Man and himself – evil tycoons and evil armour. In The Incredible Hulk, the Hulk fights the Abomination (Tim Roth). In the first Ant-Man, Scott Lang (Paul Rudd) has to fight Yellowjacket (Cory Stoll). Thor (Chris Hemsworth) keeps fighting evil gods. In Black Panther, T'Challa (Chadwick Boseman) has to fight his cousin Eric Killmonger (Michael B. Jordan) in another panther suit. If Captain Marvel (Brie Larson) hasn't fought an evil version of herself, it's not yet, and she does have a second movie coming. The Falcon and the Winter Soldier might be the most self-reflexive iteration of that trope – the entire series is founded on it.
This theme, or trope, extends to the DC movies and shows as well. In Man of Steel, Superman (Henry Cavill) fights General Zod. In Wonder Woman, Diana (Gal Gadot), a demigoddess of Love, fights Ares the God of War (David Thewlis). In Aquaman, Arthur (Jason Mamoa) fights his half-brother Orm (Patrick Wilson). In Shazam, Billy (Zachary Levi) fights Sivana (Mark Strong), who is not his superpowered opposite in the comics but a short, scrawny mad scientist. In the CW DC shows, it's become a dull cliché. In Arrow, Oliver (Stephen Amell) has fought several evil archers. Every season of The Flash demands that Barry (Grant Gustin) fight an evil speedster.
Most recently, in WandaVision, Wanda (Elizabeth Olsen) has to end the show by fighting Agatha Harkness (Kathryn Hahn), an evil sorceress who is a dark reflection of her. Who would have thought that Jung would provide the prevailing trope in superhero movies and TV shows? At best, it might be used to expose insights in the characters and stories. At worst, it can become a lazy go-to like in some of the CW DC shows. The problem is this theme or trope is fast becoming a cliché that's too easy to spot. And that might become the ultimate downfall of the superhero genre when the audience finally gets tired of predictability.
The Falcon and the Winter Soldier and WandaVision, along with all the MCU movies, are streaming on Disney+.