who is the worst person in history

from all your history classes or just people you know about from a long time ago who in your opinion is the worst for me I say genghis khan he would conquer every where he went kill or recruit the men to his army the rape the women and force them to hold his kids people say he could be related to everyone but tbh that's most likely not true people also say if some one was going to conquer the world it would have been him but who do you guys thinks the worst and also put together a back sorry about them