Zhang Xianzhong was the leader of the peasant uprising that ended the Ming Dynasty in 1644-46 and started the Xi Dynasty. The Ming Dynasty started in 1368, so it lasted several hundreds of years (one of the earliest officials was Zheng He, court eunuch and well-regarded admiral) (eunuchs were basically given powerful positions in government that sometimes superceded that of the Grand Secretaries, whereas peasants were the farmers that got treated terribly in ancient China, like the Qin dynasty with emperors like Qin Shi Huangdi).
So what was Zhang's kill count? 1 million people dead in the Sichuan massacre (caused a population collapse). Although it is heavily disputed (he was later snuffed out himself by invading Qing armies storming Sichuan). He was known to chop off the feet of his victim's and burn them in a pile. He is well-known for this one fucked up thing he said:
"Heaven brings forth innumerable things to nurture man.
Man has nothing good with which to recompense Heaven.
Kill. Kill. Kill. Kill. Kill. Kill. Kill."
To this day, the Sichuan massacre is said to be the worst one in recorded history.
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