I always felt Marx summarized the economic history of human beings very well, but that he "dropped the ball" when it came to his solution. When the communist revolutionaries took power in places like Russia, China, Cambodia, and so on, they created brutal and oppressive dictatorships which went on the tyrannize and murder their own citizens (Holodomor, Great Leap Forward, Cambodian genocide, etc). There was no accountability for government at all.
It just seems an extremely big oversight that Marx, as educated about history and political science as he was, was unable to look at the French Enlightenment, the organization of the US government at his time, or the successful constitutions of history, and not incorporate the ideas of checks and balances, civil rights, or accountability to his revolutionary government...
Marx even presided over some of the early Internationals. Why didn't he advocate a realistic form of government to avoid the rise of all these despots, the confusion of the Soviet transfers of the power, and so on? His idealism about the "dictatorship" to establish a just economic and political order just seems very naive.
First some definitions.
Proletariat:
The class of the wholly propertyless, who are obliged to sell their labor to the bourgeoisie in order to get, in exchange, the means of subsistence for their support. This is called the class of proletarians, or the proletariat.
Engels -- Principles of communism
a dictatorship of the proletariat is when the proletariat has complete political control of the state apparatus, and by this leaving other classes powerless, also during this time the state will be capitalist. He is not advocating rule by one man
remember that this is a transitional stage to communism.