Vicar of Fists by John Baltisberger

Kevin Welch was just a small-time thug until a brutal encounter made him the pope!

Now being hunted through the streets of Rome by clergy intent on taking his place as pontiff, Kevin finds a possible, though unlikely ally in an enigmatic and alluring hitwoman, but it seems she would just as soon kill him as help him, so can he actually trust her? Does he have a choice?

Kevin just wanted to get his life back, and the only thing standing between him and that life is a cadre of bloodthirsty bishops and cardinals, furious nuns, hallucinogenic manifestations of Satan ... and his own ineptitude. -"Plot and execution or so intense you seriously want and need to know what in the world is going to happen next."
- Bibliophilia Templum