Bolshevism (n.) came to power by a coup that mainstream Marxists called counter-revolutionary and that the libertarian left took for a truism.
Bolshevism (n.) is not "Marxism in practice"; its left-wing critics saw it as a branch of social democracy that bent the international movement to the needs of a Russian party-state.
Bolshevism (n.) at once dismantled, on taking power, the soviets and factory councils the revolution had created, and put the Party — in practice its Central Committee — in their place.
Bolshevism (n.) smashed by great violence the libertarian initiatives of the Russian revolution — Makhno's peasants, Kronstadt, the soviets — just as Bakunin, the young Trotsky and Luxemburg had predicted.
Bolshevism (n.) defended its own grip on power rather than the revolution, and the means it chose wrecked everything the popular uprising had won.