There are many aspects of the Marvel Cinematic Universe that have had a huge impact on the franchise, some of which stretch all the way back to Phase One, when no one could have predicted just how big it would ultimately grow to be.
Stark Tech, the Infinity Stones, and Thanos' role as the cosmic puppet master have all been threads running through the entirety of the MCU, as has the super soldier serum.
First created by Dr. Erskine during World War II, the idea was to build the USA an entire army of super soldiers. Of course, the doctor was killed before this happened, leaving his work unfinished, for a few years at least.
While it was originally believed that the serum died with him, thanks to the work of others, standing on the shoulders of the giant that was Dr. Erskine, Hydra's recreation of the serum, and some attempts that ultimately went very wrong, there have been a handful of super soldiers in the MCU.
Some of these turned out exactly how they were supposed to, while the results of others left more than a little to be desired.
8. Emil Blonsky
As a soldier, Emil Blonsky had an exemplary record. So much so that when Thaddeus Ross was putting together his team to take down Bruce Banner in Brazil, he brought Blonsky in as an ace up his sleeve. To get this man in his team was a coup of sorts, and he was far more qualified for the job than anyone else.
He was a ruthless fighter, but his inability to accept defeat ultimately led to his downfall. Blonsky first became enhanced thanks to the crude serum Thaddeus Ross gave him, essentially beefing him up enough to get a taste of the power it could unlock, but not to the extent that the true super soldier serum would.
His appetite then took him to Dr. Sterns, who injected him with the concoction he manifested from Bruce Banner's blood. In the doctor's own words, the cocktail that was now his bloodstream turned him into an Abomination. However, it wasn't long until Blonsky had his butt kicked by Banner, and was shipped off to a cryo-cell in Alaska, where it would seem that he has been ever since.
He did enough for the World Security Council to want to extend to him an invitation to the Avengers Initiative, but in the end the right botched super soldier made the team...