The Batman Who Laughs: The Full Story
2. The Secret Six
During 2019's Batman - Superman run, the Darkest Knight needed to create dark versions of the six people he needed in order to open another portal to the Dark Multiverse. He created six batarangs infused with a serum of his own creation and Nth Metal, before setting out to find his victims.
While he was briefly held prisoner in the Hall of Justice, the villain had a back-up plan already in motion. He had already infected Shazam, Commissioner Gordon, Blue Beetle, Donna Troy and Hawkman who followed our heroes to the Fortress of Solitude and launched an attack. The only person left that needed to be infected was Superman, but that part of the plan was about to take an unexpected turn.
As Superman tries to bring down the Fortress, trapping the infected deep under the rubble, Supergirl arrives to break up Hawkman and Batman. Unfortunately, her presence would be the Earth's downfall as she saves Superman from being wounded by the batarang.
The blade slices her hands and infects her, completing the Secret Six and opening a portal to the Dark Multiverse, through which The Batman Who Laughs could bring more Dark Knights to Earth Prime.