Chin Shi Huang Di epic failed. He had centuries of archives of Chinese history and wisdom destroyed to advance his "Year One" concept by starting the notion that all history would then on begin with his reign. So yeah, centuries of accumulated knowledge was thrown down the toilet, metaphorically speaking- most of it was burned, actually....
King George III, for having absolutely no people skills and not realizing that taxing colonies without allowing them to be represented in Parliament was probably not the best idea... In doing so he began what would eventually become the dissembling of the British Empire and prevented them from possibly becoming the 21st centurie's super power. So yeah, kinda screwed over his country there.
Hoover and Buchanan were flat out useless. You could have waved pictures of Hoovervilles in his face and it still would have taken the hand of God to make him 'really' acknowledge the Depression. Reagan squandered an enormous amount of money, but you wouldn't know that because most of the U.S. is still too busy glorifying his astoundingly unglorious presidency because he made them feel good about being stupid. Bush, needless to say, is and was an utter tool and to this day it astounds me that he was actually number 43.
Then there are the genocidal dipshits Hitler, Stalin, Pot, etc. And along with being genocidal dipshits they made themselves the standard with which we scale evil in our day and age and in the case of Stalin and Pot, eternally damned the world image of their political philosophy.
So yeah, all bad leaders.