Power corrupts, absolute power corrupts absolutely, and awesome power corrupts awesomely.
Granted, it probably wasn't all that awesome living under these rulers, but it's a lot of fun to read about them from afar.
6Anna I of Russia: Kind of a Murderous Tom Green
Anna I of Russia (1639-1740) was either the meanest bitch in history or one of its greatest pranksters. Or both.
This story tells you just about everything you need to know about a woman who both had absolute power and was batshit insane: She once found out a nobleman had committed the offense of marrying a Catholic. In response she forced him to marry an old hag, then after the wedding ceremony dressed them up as clowns, paraded them through the streets with farm animals, stripped them naked and made them sleep in a palace made of ice. This was in Russia in the middle of winter, where taking a piss means you instantly have an icicle jammed up your urethra.
Her reign was one of terror, both in the general sense (she started that "secret police" thing in Russia) and in the humiliating sense. Anyone who even mildly upset her knew they were either in for a cruel mocking, or a horrific death (which we suppose she thought was all part of the joke). Overcook her food? To the gallows! Speaking against her? Off with your tongue! Political opponents and general asshats alike had made her endless hit-list.
"All y'all mothafuckas betta watch yo' fuckin' selves."
When she wasn't ordering random murder, she would randomly command a person to stand in a corner and impersonate a chicken or dog or cat; anything that she liked, really. Horrible? Yes. But which of us can say we wouldn't do exactly the same if given absolute power? We at Cracked salute her, out of fear and admiration.