Steve Rogers is one of a kind, but there have still been many, many attempts in the Marvel Cinematic Universe to replicate the super soldier serum that transformed him into Captain America. Whether because of flaws in the science, poorly chosen test subjects, or ill treatment of the super soldiers who received it, super soldier serums have arguably done a lot more harm than good.
That’s certainly the opinion of Baron Helmut Zemo, who was broken out of prison in The Falcon and the Winter Soldier and temporarily teamed up with Sam and Bucky against the Flag-Smashers. Considered freedom fighters by some and terrorists by others, the Flag-Smashers have used their newfound superpowers to fight on behalf of the refugees who have been displaced in the wake of billions of people suddenly returning after the Blip. The new Captain America, John Walker, has now also taken the super soldier serum in the hopes of being as strong as Steve Rogers – and has proven that it takes more than just physical strength to be Captain America.
Abraham Erskine’s Super Soldier Serum
The original super soldier serum was created by the scientist Abraham Erskine, who hand-picked Steve Rogers to be the soldier who received it based on his scrawny body and great strength of character. Erskine emphasized that his serum enhanced not just the body, but the mind as well. “The serum amplifies everything that is inside, so good becomes great; bad becomes worse,” he told Steve Rogers. “The strong man who has known power all his life may lose respect for that power, but a weak man knows the value of strength, and knows compassion.” Erskine’s super soldier serum had to be used in combination with vita radiation in order to have safe and stable effects, so Steve Rogers was simultaneously injected with the serum and bombarded with the vita rays.
The Red Skull’s Super Soldier Serum
Erskine first began working on the super soldier serum in 1930, and when the Nazis came into power both they and HYDRA forced him to continue developing his formula for their purposes. Nazi leader and head of HYDRA Johann Schmidt injected himself with an earlier version of Erskine’s super soldier serum, but without the stabilizing effect of vita radiation the serum caused the skin on Schmidt’s face to burn and turn red, earning him his supervillain moniker: the Red Skull. Despite this unfortunate side effect, Erskine said that the serum did not fail, but did exactly what it was designed to do; just as the serum would later amplify Steve Rogers’ goodness, bravery and compassion, it amplified Johann Schmidt’s evil and lust for power. The Red Skull also didn’t consider himself a failure, declaring that he, not Captain America, was Erskine’s “greatest success.”
Arnim Zola’s Super Soldier Serum
After Erskine escaped and began developing his super soldier serum for the United States instead, scientist Arnim Zola took over the job of trying to perfect HYDRA’s version. He used captured American soldiers as test subjects for his experimentation with the super soldier serum, and one of these test subjects was Bucky Barnes. With Captain America’s help, Bucky was able to escape HYDRA’s clutches – but only for a short while. When he fell off a train and down a mountainside, it was his super soldier physiology that allowed him to survive the fall, albeit with the loss of his arm. He was returned to HYDRA, and a combination of cybernetics and brainwashing was used to transform him into the Winter Soldier.
Isaiah Bradley’s Super Soldier Serum
After the death of Abraham Erskine and the later disappearance of Captain America, the United States began trying to recreate the super soldier serum and used Black soldiers as test subjects. In the limited comic book series Truth: Red, White and Black (upon which The Falcon and the Winter Soldier is partly based), these new versions of the serum frequently resulted in horrifying deaths for the men who received them. Isaiah Bradley was one of the few test subjects for whom the serum worked, and the only super soldier who ultimately survived. He was sent to Goyang during the Korean War in the hopes that his enhanced strength would allow him to destroy the Winter Soldier, but was only successful in tearing off Bucky’s arm.
Howard Stark’s Super Soldier Serum
In 1991 a new version of the super soldier serum was developed by Iron Man’s father, Howard Stark. Before it could be used on any American test subjects, however, Howard was murdered by the Winter Soldier and the five doses of his super soldier serum were delivered to HYDRA. The serum was given to HYDRA’s elite death squad, who had “more kills than anyone in HYDRA’s history,” according to Bucky. As Erskine had warned back in the 1940s, giving the serum to ruthless killers had the effect of amplifying their lust for violence and HYDRA found that they were impossible to control. This attempt to create more Winter Soldiers was deemed a failure, and the test subjects were put on ice in HYDRA’s Siberia facility until they were eventually killed by Zemo.
Bruce Banner’s Super Soldier Serum
The American government resurrected Project Rebirth, the code name used for developing the super soldier serum, after the turn of the 21st century. Thaddeus Ross recruited scientist Bruce Banner to recreate Erskine’s formula, and Banner developed a new serum that was used in combination with gamma radiation instead of vita radiation. Unfortunately this proved to be anything but stable, transforming Banner into a giant green rage monster who became known as the Incredible Hulk. Rather than enhancing his personality, as the previous versions of the super soldier serum had, Banner’s formula had the effect of splitting his personality between the mild-mannered Bruce and the ill-mannered Hulk.