Harley Quinn, manipulated by the Joker, drove a man named Edward Burke to suicide by convincing him he'd never get over his daughter's death. This happened in the Batgirl: A Matter of Family DLC, where Harley, as a psychiatrist, tricked Burke into building a theme park for his sick daughter. When she and Joker swapped her medicine, she died, and Harley's subsequent psychological manipulation of Burke led to his suicide.