WARNING: The following contains spoilers for Harley Quinn Season 2, Episode 12, "Lovers' Quarrel," now streaming on DC Universe.
Harley Quinn's second season gave the supporting cast a lot more time in the limelight as the Justice League was missing, allowing all the villains to roam free. Still, apart from Dr. Psycho being bullied as a kid which caused him to become bitter, fans didn't really see any backstory for the rest of Harley's crew.
However, in "Lovers' Quarrel," this changes as King Shark inadvertently reveals his first kill as a kid, and it's a bloody terrifying one that explains why he's so scared of his berserker mode.
King Shark is a nice guy, even if he's a villain, with the gang dubbing him a gentle giant. Seeing him trying to avoid grisly murder and violence has been quite funny throughout, but when he does cut loose it's quite scary. But as to what informed all this, fans never knew because the only history we got was in "Bachelorette" when he returned home under the sea as part of his father's agreement for him to be married to Tabitha, a hammerhead from a rival shark clan.
There, it became clear that Nanaue was running from his past because life on land was better. In the ocean, he was bound by duty but on the surface, he could carve a life out on his own. However, as Psycho dissects his mind, it's revealed that Nanaue was indeed trying to escape a gory skeleton from his closet as he murdered his younger brother in his adolescence.
Psycho's pulling up the memories of Clayface and Nanaue, making fun of them with Riddler, thanks to his mind-control amplifying helmet. "I thought we were friends or at least co-workers with a begrudging professional respect," a disappointed Nanaue tells his ex-ally. When he extracts Shark's memory, he's seen playing with the kid a bit roughly while their dad, the Shark God/Kamo, oversees. However, as he picks on his sibling, he shoves him to the seafloor and the poor lad hits his knee on a rock, which causes him to bleed. Instinctively, the scent of the blood caused Nanaue to go insane and he devours his brother. Their dad tries to stop it but it's too late as Nanaue is quick with his appetite, leaving Psycho and Riddler shocked at how dark his traumatic was.
"I thought we were gonna see you crap your pants but that is dark man," exclaims Psycho, who had ironically just teased King Shark about his eating habits. They'd get interrupted by Darkseid before they could continue picking Shark's brain but this also foreshadows what's to come later when Harley cuts Wonder Woman and Shark decides to go after her. Only this time, he's under Psycho's spell, but still, one has to figure the blood would have sent him crazy. It seems this is why his dad has shown resentment towards Nanaue and hopefully, they resolve this problem soon as Shark clearly feels guilty.
DC Universe's Harley Quinn stars Kaley Cuoco, Lake Bell, Diedrich Bader, Alan Tudyk, Rahul Kohli, Christopher Meloni, Tony Hale, Ron Funches, Wanda Sykes, Natalie Morales, Jim Rash, Giancarlo Esposito, Jason Alexander and J.B. Smoove. New episodes air on Fridays.