In all honesty I've got to say Cato the Elder. This Roman leader decided it was time to absolutely destroy Carthage, just across the Mediterranean from Rome. After three wars, all of which Rome won, Cato decided he had enough and pushed his military to slaughter every remaining Carthagian. After fertilizing Carthage's soil with its inhabitants' blood, it's said that he went so far as to order his troops to sow the fields of Carthage with salt so that no plants could take root or survive. Yay Cato the Elder.