I would get rid of human nature and replace it with something else. Anything other than what it is now would be preferable.
The control freaks of the world (and there are millions) who wake up every day and desperately want to tell others what to do, how to live, etc. They do what they do in the guise of religion, charity, politics, government etc., and their goal is not to help their fellow humans but simply to control them for its own sake to enhance their own feelings of self-worth and power. They have caused untold human suffering throughout history from the cruelest dictators to the myriad demagogues who latch onto any and every "cause" to get that precious control. They are the true evil in the world; everything else pales by comparison.
Classic. Dependence / demand on oil. Seems like wars and conflicts have been going for centuries now because of it.