The regimes are examples of times communism has actually been implemented in practice.
Not the only times. Did you even glance at the YT video I linked you? I'm not a tankie. I was not referring to any ML dictatorships when I mentioned beneficial implementations. Get this through your head.
Moreover the lack of hierarchy is probably the prime reason pure, unadulterated communism can’t work. People need a leader if they’re going to be living in a large group.
[citation needed]
Notice how it says “derived from”, not that he founded it.
An ideology "deriving" from a person and being founded by that person are synonymous. Furthermore, even if we want to make a distinction between those two terms, communism predates Marx.