- There is a MEH candidate for each of Katz's appearances, as he's a Serial Killer played straight in a kids' show. In his first appearance, he ran a Hell Hotel where he fed his guests to man-eating spiders.
- Eustace crosses this in "Ball for Revenge" when he gathers up many villains to kill Courage over a blanket and even puts Muriel in harm's way (and puts her laundry on the rough setting) to force Courage's hand. That is, if he didn't cross it in "The Magic Tree of Nowhere," when he — despite flat-out talking with said Tree, thus proving its sentience — chops it down solely because it was providing for Muriel more than he could.
- If one takes the Word of God into account, Eustace potentially crossed this before the series even began. Muriel used to pine for someone else rather than Eustace, but through some "dark, unknown deed", somehow he wooed her over instead. Considering how dysfunctional their marriage is and that Eustace does everything in his power to exploit Muriel for his own benefit, this makes him dangerously realistic for a Jerkass that wanted things his way.
- Mad Dog trying to run over Bunny and Courage.
- The vet sending Courage's parents to the moon For Science!.
- Le Quack is not only ready to assault old people to break into their houses and steal all valuables but also has a bad habit of slaughtering whoever stands in the way of his freedom.
- Fusili has increased his collection of puppets through innocent every day people and enjoys playing with their puppet-dead bodies and reenacting what they did in life.
- Shwick was wanted for many disappearances, in other words he fed quite a few people to his monster behind the door.
- The Queen of the Black Puddle has feasted upon many men by using her supernatural charms to lead them to their doom. Whoever followed ended up as a grinning skeleton in her garden of death.
- Ma Bagge abused and neglected Eustace through most of his childhood. Bad enough, but far from her only candidate. In Bad Hair Day he kidnapped and experimented on people for her firm, in the Mc Phearson Phantom she planned with the titular phantom to cripple Eustace and frame Muriel, intended to abandon the Bagges to a sand-whale in The Sand Whale strikes and attempted genocide against an underwater population of little creatures for her firm's sake in Scuba Scuba Doo.
- Di Lung has proven himself to be a total sociopath, when he had his robot brutally beat up Courage, kicked him in a manhole out of spite in another episode and also removed Muriel's bones for a dark ritual, laughing while he did it.
- Vastabael Backjurius from Mission to the Sun gets a big one. He takes over Muriel's mind and tries to sabotage the mission of keeping the sun from going out, which will kill all life on earth. But not before messing with Muriel's personality and body for fun. He also tries to kill Eustace and does it all with a sadistic laugh.
- Plus, there's the Cajun Fox who is obsessed with cooking...he kidnaps Muriel and attempts to use her as a final ingredient.
- There is also Benton Tarantella from "Everyone Wants to Direct". The sadist zombie who is actually a former serial killer who, with help from his partner Errol (who was pretty bad himself too), posed as an amateur filmmaker wanting to direct in his victims homes. After they let the two in, they would kill them. Now he plans to bring Errol back to life so they could continue their killing spree, starting with Muriel and Eustace, obviously.
Moral Event Horizon / Courage the Cowardly Dog