How The Super Soldier Serum Changed Bucky (What Was Amplified)

With super soldiers becoming more common within the MCU in The Falcon and the Winter Soldier, the series emphasizes that the Super Soldier Serum first developed by Dr. Erskine in Captain America: The First Avenger bestows people with super strength and amplifies what’s already inside of them. But how exactly was Bucky Barnes (Sebastian Stan) changed by the serum? Apart from his obvious super strength, the effect that the serum has on Bucky’s personality is rather unclear since the Captain America franchise focuses more on Bucky’s Hydra brainwashing and journey as the Winter Soldier. After Bucky's Hydra brainwashing is deprogrammed by Shuri, however, The Falcon and the Winter Soldier is able to explore more fully which of Bucky’s traits the serum amplified.

When Dr. Erskine first tells Steve Rogers (Chris Evans) about the serum’s effect on Red Skull in The First Avenger, he states “the serum amplifies everything that is inside so good becomes great. Bad becomes worse.” The First Avenger presents Rogers and Red Skull as extreme opposites whose inherent personality was increased by the serum, with Steve as the epitome of good and Red Skull the epitome of evil. In The Falcon and the Winter Soldier, however, that black-and-white thinking is discarded and those test subjects who receive the MCU's super soldier serum are presented with more complexity. Karli Morgenthau’s anger towards governments and kindness towards the masses cause her to lead the Flagsmashers after she takes the serum. John Walker’s temper and pursuit of justice caused him to kill an innocent Flagsmasher after he's injected. Similarly, Bucky’s actions in The Falcon and the Winter Soldier show that the serum increased both good and bad traits within him.

Bucky’s most defining trait is his loyalty, especially to his best friend Steve. In The First Avenger and Captain America: The Winter Soldier, it’s revealed that Bucky was like family to Steve since he comforted him after his parents' deaths, defended him against a heckler, and became his right-hand man within the Howling Commandos. Even Bucky’s most iconic quote “I’m with you 'til the end of the line” displays his familial bond with Steve. That same loyalty appears to be one of the traits amplified by the serum since Bucky makes it his mission throughout The Falcon and the Winter Soldier to preserve Steve’s legacy as Captain America. When Walker is unrightfully handed down the shield, Bucky vows to take it back from him and give it to Sam (Anthony Mackie), as Steve intended. Bucky’s loyalty becomes so extreme that he initially gets mad at Sam for retiring the shield since he views it as his last connection to Steve.

Captain America's shield bucky and sam in Falcon and Winter Soldier

The serum also amplifies Bucky’s sense of justice, which is demonstrated in The Falcon and the Winter Soldier through Bucky’s act of “avenging.” In The First Avenger, Bucky was a member of the Howling Commandos, an elite squadron of P.O.W. survivors that Captain America rescued from Red Skull’s Hydra base. In The Winter Soldier, Steve admits to Nick Fury that the Greatest Generation sometimes compromised “in ways that made us not sleep so well,” which insinuates that he and his fellow SSR soldiers sometimes had to achieve justice through dishonorable means. When Bucky is shown threatening the Hydra supporter Senator Atwood in episode 1 of The Falcon and the Winter Soldier, that method of doing something immoral to achieve a greater good appears to be aligned with his experiences in the war and the justice that motivated him as a soldier.

That thin moral line between what he did in the war and the assassinations he committed for Hydra as the Winter Soldier may also explain Bucky’s internal struggle introduced in The Falcon and the Winter Soldier. In episode 2, Bucky admits that he’s worried that Steve may have been wrong about him being a good person. If the serum is meant to amplify what’s good or bad inside of someone, and Bucky became the Winter Soldier shortly after being injected, it’s enough to make him question how much of his behavior as the Winter Soldier was due to Hydra’s influence or his own innate qualities that the serum amplified.

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