He was, by all accounts, as you say, the perfect asshole, cruel, scheming and self centered. Even by the standards of the day. If I recall correctly, Pope Alexander VI, Borgia (father - and probably more - to Cesare and Lucrezia) was Pope. There was a phenomenon in Rome called the Borgia Flu - pretty much any death where the cause wasn't real, real obvious, was blamed on that trio.

People who assasinated each other and slaughtered each other's peasants and financed the Spanish Inquisition and turned each other over to it anytime it was profitable to do so considered him a cruel, scheming, self centered asshole. When he was dragged back from the New World in chains, it was because he managed to turn the stomachs of people who considered the Spanish Inquisition as kindly helping sinners reform, and were not at all ignorant of the methods.