10 Times The Past Came Back To Haunt Batman
3. Joe Chill - Batman #35-40
During the Endgame saga, Joker concocted a Joker Venom that causes the infected person to have murderous tendencies to anyone they love. Batman deduced that the cure could be extracted from the cells of the first person Joker infected with the toxin.
Batman managed to locate Patient Zero but was astounded to learn it was Joe Chill, the man who killed Bruce Wayne's parents. Not only was it haunting to come face-to-face with his parents' killer, this meant that the Joker knew of Batman's identity! The Joker could've chosen absolutely anybody to infect with his Venom but chose Chill solely to mess with Batman's mind.
The Joker then orchestrated Chill to recreate the murder of the Waynes by shooting a family called the Thomases. Batman tries to reach Chill before he pulled the trigger but he and the Thomases were behind a pane of glass. Out of desperation, Batman shattered the pane and grabbed Chill's gun before he shot the Thomases.
However, breaking the glass caused the Thomases to be exposed to the Joker Venom, causing them to become irreversibly insane. Although Batman adopted the Thomas' son, Duke, he had to accept that Chill had, once again, destroyed a child's life.