Paul ruled from 1555 to 1559; he's called the Father of the Roman Inquisition. The Inquisition was an attempt to root out Protestantism, as well as consolidate Papal power in Rome - Paul learned his dirty tactics while serving as nuncio in Spain.

As if this weren't bad enough, Paul also created a Jewish ghetto inside Rome, and forced Jews to wear special yellow hats. He made a habit of banning books.