system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU] Why did the serum not mutate anybody else?

The serum mutated Red Skull, giving him his name, because he was a bad person, and that makes you mutate with the serum, and thats why it was so important to give a "good person" the serum. 

But there's been other people who got the serum that weren't exactly good people, like the Flagsmashers and Red Guardian. Why didn't they mutate?
gpt
Where did you get your info from?

The serum red skull got was a prototype and obviously had some side effects as a result, the one Steve got was the perfected version and the flagsmasher version is made using whatever information survived of the original serum with some modern technology to fill in the blanks.