Victor "Mister" Zsasz is an actual comic book character who made his debut in June 1992 in Batman: Shadow of the Bat #1. His trademark is cutting a number/tally on his skin for each victim he kills.
In this series, Anthony Carrigan plays Victor Zsasz, a DC Comics villain. He also plays a different villain in The Flash (2014), another DC Comics franchise.
Anthony Carrigan, who pays Victor Zsasz, has a medical condition called alopecia which caused his complete hairlessness by age 30. Despite his initial struggles with his self-image, he now speaks openly about the power of body positivity.