Warning: This list contains discussion of extreme violence and sexual assault.
Heroes are nothing without their villains, and that is especially true under the DC Comics banner. How much the audience loves its protagonist is often decided by how much it hates the antagonist. When it comes to the "heels" of DC, they offer plenty of reasons for readers to hate them.
DC Comics has a tendency to go darker than its superhero universe counterparts, and that darkness offers more opportunity to deliver stories where the villains can be downright despicable. Rather than just plant bombs or indulge in cartoonish plots, DC's villains often commit despicable, even disgusting acts of villainy. Batman's rogues gallery alone is a threat to the entire DC Universe, but the universe at large is filled with grimy evildoers who have committed crimes that would make anyone clutch their pearls.
10 The Joker Tortures the Gordons
Batman: The Killing Joke by Alan Moore, Brian Bolland, John Higgins, and Richard Starkings
The Joker's shenanigans alone could make up the entirety of the most heinous things to happen under the DC Comics banner. This instance, though, has been argued to be his most heinous of them all - so heinous that this originally out-of-continuity one-shot, The Killing Joke, was canonized simply because the Joker's brutality was as unforgettable as it was unforgivable.
The Joker first surprises Barbara Gordon with a bullet through her abdomen and spine, effectively retiring her as Batgirl and paralyzing her. The Joker doesn't stop there, as he strips Barb naked whilst taking photos of her, which he shows to her dad while torturing him. These crimes were all in an effort to show that anyone could turn evil after one bad day. It didn't work on Jim Gordon, but it mentally scarred both the Commissioner and his daughter.
9 Black Mask Makes Catwoman’s Sister Eat Her Brother
Catwoman #15 by Ed Brubaker, Cameron Stewart, Matt Hollingsworth, and Sean Konot
Black Mask concludes that Selina Kyle has meddled in his mob's plans one too many times. When Roman Sionis gets mad, he doesn't just get even - he gets vindictive. So, in an effort to get closer to getting his hands on Catwoman, and to get a modicum of payback, he captures Selina's sister Maggie and Maggie's husband, Simon. He tortures them, but torturing for Black Mask isn't just beating or maiming his captives.
For a person as twisted as someone with Black Mask's origin story, torturing Maggie Kyle calls for him to cut out her husband's eye and then feed it to her. Catwoman arrives in the next issue to save her sister, and she even kills Black Mask, but after digesting her husband, Maggie looks far too disheveled to enjoy her freedom.
8 The Penguin Ruins a Chef's Life
Joker's Asylum: Penguin #1 by Jason Aaron, Jason Pearson, David McCaig, and Rob Leigh
Oswald Cobblepot notoriously has an inferiority complex. So, when he's having dinner at Le Fou Frog with his new sweetheart, Violet, he takes it personally when he hears the chef chuckle while the Penguin is expressing his love for her. The chef may not have even been laughing at the Penguin, but it didn't matter to Cobblepot. In his head, he had an excuse to be as wicked as possible.

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Within days, the Penguin bought out the building, fired all the restaurant's employees, closed it, had the chef's girlfriend deported to Romania, and his best friend framed for felonious crimes. It didn't stop there. The chef suddenly had a noisy neighbor, his church infested with bees, and his favorite park bulldozed. In addition, the ex-alcoholic chef had to contend with a 24-hour liquor store that suddenly opened across the street. The chef hanged himself within two months. The Penguin giggled at his obituary, clipping it into his scrapbook.
7 Two-Face Outed Renee Montoya and Framed Her for Murder
Gotham Central #6-10 by Greg Rucka, Michael Lark, Matt Hollingsworth, Lee Loughridge, and Willie Schubert
Two-Face has toyed with the idea of redeeming himself in the past, but when readers his dirt sheet, a redemption arc is easier said than done. Once, he harbored an unrequited love for Renee Montoya: a lesbian, so that was never going to happen. Two-Face never let the rejection go, though, and flipped a coin in order to concoct a plan to ruin her life.
Detective Montoya walks into the GD offices and a picture of her kissing her partner is plastered on the bulletin board. Montoya was outed in an era where it was even more dangerous to be gay, and her problems only persisted. News of her orientation eventually leads to her parents disowning her, and worse, she's framed for murder, then kidnapped by Dent. Two-Face orchestrated everything, hoping if Montoya lost everything (her family, career, reputation, etc.), she'd have no choice but to choose him. She still said no.
6 Poison Ivy Imprisoned Count Vertigo as a Sex Slave
Suicide Squad #46 by John Ostrander, Kim Yale, Luke McDonnell, Geof Isherwood, Todd Klein, and Tom McCraw
For audiences to fully embrace Poison Ivy as a hero, DC Comics has had to make sure everyone forgets her more diabolical actions. As a villain, she was far more than just a plant sympathizer and eco-terrorist. Her dynamic with Count Vertigo was living proof of how evil she could be.
After the Suicide Squad disbanded, Vertigo was captured and drugged by the Vlatavan rebels before being captured, in turn, by Ivy. Taking advantage of his bipolar disorder and his drugged state, she further disturbed his mind by frequently dousing him with mind-controlling elixirs, turning him into her personal slave for at least a year. Before Amanda Waller saved him, Ivy did such unspeakable things to Vertigo, that he grew to hate her and wanted to end his life as a result of the physical and mental torment.
5 The Joker Blows Children Up
Batman: Cacophony #1 by Kevin Smith, Walt Flanagan, Sandra Hope, Guy Major, and Jared K. Fletcher
Upon escaping Arkham Asylum, The Joker crosses paths with Maxie Zeus: Gotham's goofiest (yet tragic) villain, who is merely a history professor who studied one too many Greek myths. He makes Greek mythology his entire personality, in more ways than one. Before being imprisoned, the Joker gave Maxie the funds and the drugs to randomly Jokerize citizens of Gotham to pull an elaborate April Fools' Day joke on Batman. Maxie strays from the plan, instead using it all to fund a public school whilst becoming Gotham's newest kingpin.
The Joker isn't happy, and upon his release, seeks to punish Maxie. He does so by blowing up the school while it is still full of children. The Joker doesn't just get revenge on someone who wrongs him, but he does so with a smile on his face whilst laughing and running away from the chaos.
4 The Riddler Poisoned Kite-Man’s Son for Spying
Batman #27 by Tom King, Clay Mann, Danny Miki, John Livesay, Gabe Eltaeb, and Clayton Cowles
"The War of Jokes and Riddles" story arc during Tom King's Batman run presented an origin story of sorts for the Joker and the Riddler's feud, which then sparked their relationship with Batman. In addition, this story provides a heartbreaking origin for Kite-Man. Charles "Chuck" Brown was hired by the Joker to the Riddler's crew and spy on him as an informant. Unfortunately, Edward Nigma saw right through that guise and immediately sought ways to punish Chuck for his ruse.
In retaliation, he laced with poison the rope of a kite that Chuck's son was playing with, promptly hospitalizing and killing the boy. The Riddler treated an innocent boy's life as not only a message to his opposition, but as a riddle and a game. Losing his son snapped Chuck into a fit of vengeance, devising an identity to kill the Riddler: Kite-Man. His "Hell Yeah" catchphrase also stems from honoring his son, who feared he was dying as punishment for saying a bad word that would send him to "that other place."
3 Harley Quinn Bombs Children
Detective Comics #23.2 by Matt Kindt, Neil Googe, Wil Quintana, and Taylor Esposito
Much like the love of her life, Poison Ivy, Harley Quinn's redemption arc doesn't make sense once people the kind of horrible things she was up to as a villain. Among those horrible things was having a video game's software updated with an explosive bomb that would activate in the hands of any Gothamite holding the portable device on the same night, many of whom were children.
DC has always been transparent about how complicated it is to frame Harley as a hero today after her past, to the point that the Justice League still don't trust her. Most stories build on the quirkiness of Quinn and her willingness to change to help endear her to an audience, but Quinn looks a lot less endearing when audiences that she's killed children without remorse.
2 Bane Kills Alfred in Front of Damian Wayne
Batman #77 by Tom King, Mikel Janín, Tony S. Daniel, Norm Rapmund, Jordie Bellaire, Tomeu Morey, and Clayton Cowles
During the "City of Bane" arc from King's Batman run, Bane solidified himself as the only villain to break the Bat by taking Gotham for himself. With the city under his control and Bruce Wayne missing in action, Bane warns that if any of the Bat-Family ever return to Gotham soil, then he will not hesitate to kill his hostage, Alfred Pennyworth. Out of spite and stubbornness, Robin did not heed that warning, so when Flashpoint Batman Thomas Wayne finds and apprehends the boy, Damian Wayne is gifted a front-row seat to see Bane snap the butler's neck.
This story is not the first time that Alfred's life was in danger, so it's natural for Robin (and even readers) to underestimate the severity of the stakes. Damian is proven wrong in the worst way possible. It's bad enough that the heart of the Bat-Family is murdered, but doing so in front of the family's youngest member to send a message is just cold.
1 The Joker Hires Robin’s Mom to Betray Jason Todd Before Beating and Killing Him
Batman #426-428 by Jim Starlin and Jim Aparo
The murder of Robin Jason Todd is often brought up as one of the worst things that the Joker has ever done to Batman, but the moment is far harsher than some may . It starts with Robin learning that the woman he long thought was his mom actually wasn't. His biological mother is Dr. Sheila Haywood, who works in an Ethiopian medical relief camp. Jason travels to meet her, but the Joker makes the trip to Addis Ababa, Ethiopia before Jason can.
The Joker frames Sheila, manipulating her into turning her son over to the Clown Prince, who proceeds to beat Jason with a crowbar. Then, with Jason and his mother chained inside, the Joker bombs the warehouse while Batman watches helplessly. The Joker loves to add insult to injury by adding crimes on top of crimes, and trauma on top of trauma. This scheme in particular ranks among his most elaborate, and unforgivable, in DC Comics history.