He wasn't a marxist

I think he was a corrupted version of a Marxist that was influenced heavily by Marxism but didn't have his priorities straight. His main problem was he was unable to handle power without going nuts thanks to his sociopathic tendencies.

Lenin was corrupt too

Yes, but not as much as Stalin. Even if Lenin stayed in power though the USSR was doomed because Lenin was surrounded by corrupt jackels who either didn't understand or didn't truly care about socialism.

the entire concept start-to-end of the Bolsheviks (as opposed to the Mensheviks) was to make a corrupt state

I don't agree, I think Lenin was a genuine Marxist but his party was infested with fake Marxists and pseudo-socialists. I do agree that the Mensheviks were better though, not because they were less radically socialist (which they were) but because they were more democratic and less authoritarian.

Every single time Communism happens this is the case.

Every single time communism happens it's not communism and it is made to look even worse by it's ideological enemies.

Only Cuba and Vietnam have ever achieved a remotely humane form of it

Most of what went wrong in those countries is America's fault directly because of the economic and military interference. America is a country that treats it's own moderately well (while screwing them over in ways that are more subtle and lawlessly dealing with the few individuals who truly threaten the establishment behind closed doors) but is outright fascist in it's treatment of other nations that it occupies and bullies. When it comes to it's treatment of small, poor nations, America is the most evil country that could possibly exist. If you dare to attempt socialism it will barricade you economically, try to make sure the most corrupt leaders are elected, and ignore the fact that your country was small and poor to begin with while it blames every single "failure" and injustice that happens on socialism.