Before the French Revolutionary Red Terror, the Spanish inquisition, which killed a dozen or so people every year, was the standard evil example of repression, and Queen Bloody Mary, who murdered a couple of hundred and caused a thousand or so to flee, the classic tyrant.
That's probably attributed to the parochialism of Bretons of the era -- they couldn't know about the Yangzhou massacre in China where 800,000 people were slaughtered, and the Massacre of the Latins in the 12th century in Constantinople wouldn't stick in their minds.
Those incidents were war, not repression. You need to compare twelfth century repression with twentieth century repression, and twelfth century war with twentieth century war.
Modern repression is enormously more violent than ancient repression. Modern wars are larger and bloodier than ancient wars. Incidents where the populace of a vanquished city were massacred may be less common in modern wars, but if so this may be because we can accomplish the same effect more efficiently by such means as were employed at Dresden and Hiroshima. If you flatten a city before you take it, this discourages resistance more effectively than slaughtering a city that stubbornly resisted for an unreasonably long time.
I wanted to bring attention to two posts from Razib Khan's Discover magazine gene expression blog (some of you may have been readers of the still active original gnxp) on the polemic surrounding Pinker's The Better Angels of Our Nature.
Relative Angels and absolute Demons (and the related But peace does reign! )
I generally agree with some of his arguments, but found this quote especially as summing up some of my own sentiments: