Alright, here's a fairly dark one.
Alexei Gastev (1882-1971)
In spite of the infamy he holds in the history textbooks, Alexei Gastev was once a fairly obscure Accelerationist politician in the Russian successor state of Zheltorossiya. However, following a series of political crises, he launched a coup and gained control of Zheltorossiya. Thus, the unstable republic became a dictatorship of an truly unprecedented variety.
Once in charge, he proved not to be any ordinary sort of dictator. Rather, he became an existential threat to human society and freedom as we know it. Under his crazed rule, names were to be abolished and replaced with numbers, and the family was destroyed. The freedom of the citizens was limited as much as possible in every way.
In spite of its apparent insanity, the One State was able to conquer much of Russia and China. Indeed, the rogue state seemed poise to extinguish human society as we know it. However, following the invention of nuclear weapons, Gastev ended his campaign of expansion and chose to begin consolidating power within the territories he already governed. Following the end of the One State's expansion, Gastev then ruled his nightmarish totalitarian domain until his death at the age of 89.
After Gastev's death, the One State came under the rule of a faceless council of bureaucrats and scientists. To this day, the One State is widely deemed to be the worst government to have ever existed in the entirety of human history.