Queen Sowawondra of Sumtri had more than thirty thousand people put to death during her reign. She was described as "quite touchy". Her later successor Queen Zazumba is said to be less temperamental so long as the imports of cosmetics, toiletries and clothing keep coming.
Possibly the most bloodthirsty female monarch in Roundworld history was Queen Ranavalona of Madagascar, who in the middle nineteenth century is thought to have cumulatively massacred 150,000 people (generally for that recurring African reason: they belonged to the wrong tribe). She was eventually deposed by the French, who saw this as the ideal reason to add Madagascar to their empire.
Her outstandingly-preposterous full name (as if Ranavalona wasn't long enough) was Rabodoandrianampoinimerina.