During his time as an inmate, Luke Cage was experimented on to recreate the Super Soldier Serum that gave Captain America his abilities by Doctor Noah Burstein.
The original Super Soldier Serum was created by Abraham Erskine (Stanley Tucci) while he was still living in Germany before escaping to America to get away from the Nazi party. Of course, we've all seen the movie, we know he went on to perfect his formula and give it to Steve Rogers.
Alongside her rigorous training, Natasha Romanoff also has super-soldier serum pumping through her veins. This version of the serum does not grant her the same strength as Captain America, but it does allow Natasha to perform at peak human condition in regards to her stamina and strength.
Artificially Enhanced Physiology: Due to being injected with a prototype version of the Super Soldier Serum that was given to Captain America, his physical and mental abilities have been enhanced to beyond the peak of human potential, although some of his abilities may have dwindled with age.
Although Bucky has come a long way in his recent MCU appearances, his history as the Winter Soldier disqualifies him from ever becoming Captain America. Throughout the entire Cold War and beyond, the Winter Soldier operated as a Hydra assassin, killing numerous American operatives during that time.
Sam also knows that Captain America (the proper one) is an exception, not the rule. Super soldier serum amplifies the qualities of those who take it, so unless the recipient is an absolute bastion of moral fortitude like St. Steve, the effects can be unpredictable.
Nick Fury's Wife Is a Skrull, and He's Okay With That. Fury's wife, Varra worked for the rogue Skrull faction led by Gravik, which Fury was unaware of. Their romance was always an arrangement. Priscilla, Fury's wife, survived the Snap and mourned his absence for five years.
Wade Wilson is a mutant who was part of the team Team X. He eventually quit the team, only to be brought back in against his will and experimented upon by the combined efforts of William Stryker and his lieutenant Francis, becoming a deranged, immortal super-soldier labeled Weapon XI.
there has never been any mention or insinuation that the process sterilized Steve, and there have been alternate universe versions and what if versions that did have kids who often went on to become heroes themselves.
The subsequent 1991 Weapon X storyline established that Wolverine had received the adamantium grafted to his skeleton in a tortuous process conducted by a secret government project intended to create a super soldier, and that this experience led to post-traumatic amnesia.
Bucky owes his youthful appearance to repeated cryo-freezes orchestrated by the Russians. He possesses no super powers and never received a form of the Super Soldier Serum as many assume, but continues to operate at peak human ability.
Enhanced Strength: The Winter Soldier has strength that is equal to that of Captain America. Bucky's strength was greatly boosted by a serum given to him by HYDRA scientists. The Winter Soldier's physical strength is enhanced to superhuman levels.
Serum enhances the strength and ability of human. Now bucky was not weaker than John, but we can see the fact that even at his human level John walker had better training than Bucky. He was so good as fighting before even getting the serum. So he was able to fight better than bucky.
Fury was able to fake his death by taking a drug that slowed his heartbeat to one beat a minute. It was enough to fool Steve Rogers, Maria Hill, and Black Widow. By faking his death, Fury could covertly work with Captain America to bring down the infiltration of HYDRA agents into SHIELD.
But, with inspiration from his grandfather and a drive to do good at all costs, he distinguished himself in a military career to earn the rank of Colonel and be appointed director of the Strategic Homeland Intervention, Enforcement and Logistics Division, the intelligence agency better known as S.H.I.E.L.D.
Popverse has been suspicious for some time, and the episode 'Beloved' confirmed it - James Rhodes is a Skrull. That's right, the same Rhodey who has fought alongside the Avengers as War Machine. Rhodey's behavior in the past few episodes has raised some eyebrows, including the moment where he fired Nick Fury.
In episode 4 we learn that, sometime in the recent past, the rebellious Skrull faction kidnapped Avengers member and long-time Iron Man friend Colonel James Rhodes, also known as Rhodey, and put a Skrull in his place.
Nick Fury is the director of S.H.I.E.L.D., the spy agency tasked with keeping an eye on super-powered threats. He is an ally of the Avengers and a recurring character in the first two seasons.
For the most part, Sam Wilson was chosen to be the next Captain America in both universes for the same reason: His strong friendship with Steve Rogers and his consistent career as a genuine hero more than earned him the right to wield the shield in Rogers' mind.
In an alternate 1949, Carter was met by Rogers after completing his tasks. They lived a happy life together and were married. Steve still wore his wedding band when he reunited with Sam Wilson in 2023, but Steve chose to keep the details of his life with Peggy to himself rather than sharing them with his old friend.
In the comics, the impetus for Rogers passing the mantel on to Sam Wilson is that his serum is neutralized. This causes Rogers to age rapidly and he appears as the old man he would have been if not for the super serum halting his aging.
