"Mad City: The Gentle Art of Making Enemies" is the fourteenth episode of the third season of Gotham. It aired on January 30, 2017.
With Jerome on the loose with one target in mind, Bruce and Alfred's safety is compromised. Meanwhile, Gordon's uncle Frank pays him a visit, and Nygma and Penguin are forced to confront their issues face-to-face, with possible deadly consequences.
The episode takes inspiration from the acclaimed comic book Batman: The Killing Joke by Alan Moore.
Bruce Wayne decides to spare Jerome's life and makes a promise that he will never take a life. This is a major part of Batman's character in the comic books as well as many other adaptations of the character.
Jerome refers to Bruce Wayne as "darling", which is most likely a reference to Joker calling Batman "darling" in The Dark Knight Returns.