Isn't the "communist orbit" the only possible result of applied Marxism? I think history has basically proven that in order for a communistic regime to operate, brutal oppression is the only possible reality. Are there any counter examples?

If they're Marxists, then I'm not.

Marx had serious problems with people putting words into his mouth.

Lenin's State Capitalism was his attempt at "a merger of capitalism and socialism," which was just about all Marx had ever said about what communism would be.

Mao Zedong's Great Leap Forward also had little to do with Marx, other than being an attempt to capture Marx' admiration for capitalism's industry and productivity through a quite peculiar interpretation of socialism.

And Stalin's purges were just paranoid politics. Marx did, at one point, suggest a dictatorship of the proletariat, but he was only talking about the state managing the socialist economy long enough for it to establish itself. He wasn't interested in surveillance states, secret courts, or show trials.

For Marx, communism was just a future political-economic system which he believed to be a historical inevitability. He never provided an explanation of, and wasn't really interested in, what that system would actually look like. Marx saw socialism as the next step in history, not communism, and, in any event, Marx was far more interested in understanding capitalism than he was in describing what socialism was or what communism would be.

As for countries that have adopted Marxist policy successfully, you might want to look at some of Northern and Western Europe's social democracies and social market economies. Right up until they were deregulated, they worked pretty well.