Vietnam I guess is probably the best real world example of success.

Yugoslavia but take away all the Yugoslavs

For whatever reason communism has almost exclusively been adopted by countries who were not or were currently struggling through the early stages of industrialization. Marx and his vision for a communist society was definitely not meant for a agrarian society as it was almost exclusively attempted in.

Because Marxism-Leninism proposed that if you have a small group of people who hold all the power, you can just will your way past the bourgeois democracy stage with the help of the peasantry, and the Soviet Union put a great deal of effort into supporting ML movements, and crushing non-ML leftists.