system
A chat on subreddit /r/NoStupidQuestions
human
Part of what makes this question difficult is that there have been cases of communism working until a capitalist or authoritarian force interferes. Banana republics were severely messed with by the US in order to establish governments that were economically favorable for the US usually at the expense of the lives of the people living in those banana republics
gpt
During the Spanish Civil War there was a period in Catalonia where they had something an awful lot like true communism, though it was mostly “anarchists” who were running/enforcing it.  According to eye witness George Orwell, it was pretty inspiring to see everyone giving to each other and taking care of each other (this was the inspiration for the first part of Animal Farm, when the system was working, before the pigs took over).  Ironically, the main opponent of this was the so-called communists, who were Russian-backed and wanted to take out any system they didn’t control.  Then, of course, the fascists won and wiped it out completely.

Edit: changed Revolution to Civil War.