* The fact that [[HeadlessHorseman Celty's headless.]]
* Episode 2, "A Lie and a Truth". People who were trolled or scammed online and nearly paid their lives for it will understand.
* In the episode "Takes A Sudden Turn", during a forum [[spoiler:Saika induced victims]] start posting various disturbing comments, and the "trolls" can't be blocked off the forum. Suddenly the comments from the trolls start to rabidly post the same comment over and over while Kanra and all the others on the forum are noting its creepiness factor. What did the comment say? "Mom. Mom. Mom. Mom. Mom." This was going on while Anri was getting beaten up by several students. To make matters worse, the Slasher shows up....
* The PsychoticLoveTriangle between Seiji, Namie and Mika.
* Izaya, [[DracoInLeatherPants once you get over his charm.]]
** In the anime, his whole orchestrated kidnap of a young girl and attempt to convince her to kill herself.
** Taken UpToEleven in the novels and the manga. His [[http://i23.mangareader.net/durarara/4/durarara-1196081.jpg extremely sadistic]] [[http://i18.mangareader.net/durarara/4/durarara-1196089.jpg facial expressions]] [[http://i5.mangareader.net/durarara/4/durarara-1196083.jpg in the latter]] are ''[[NightmareFace terrifying]]''.
* Shizuo's [[TheBerserker rages.]] We're talking about a guy who can lift vending machines out of the ground with ease. And when he is having a particular bad tantrum, he tends to throw heavy objects into the street, which more than likely has either killed or injured random people.
* [[spoiler:Erica and Walker's... [[TortureTechnician other hobbies.]]]]
** [[spoiler:Again, [[https://i.imgur.com/5HlECIL.jpg it's worse]] [[https://i.imgur.com/9EdUNLX.jpg in the manga]]. Warning: NOT for the weak at heart.]]
** The worst part of it, in the anime at least, is that [[spoiler: while Erika and Walker are getting ready to do their thing, they're told not to use gas in the back of the van again (implying that they've done that at least once, and probably more times than that, if there needs to be a repeated warning). And they start brutalizing some poor schmuck while their friends just stand off to the side and drink milk]].
* [[spoiler:Anri, Saika and Saika's children.]]
** [[spoiler: Saika also has a huge Rape Is Love mentality.]]
* [[spoiler:[[BewareTheNiceOnes Mikado]] and by that token, [[CuteAndPsycho Aoba.]]]]
* [[spoiler:[[ColdBloodedTorture Earthworm.]]]]
* [[spoiler: Haruna Neikawa. Without a shadow of a doubt]]!
* When Seiji suddenly smashes Mika's face against the wall when she takes a glimpse of Celty's head.
** Mika ends up getting plastic surgery to fix her injuries... and makes herself look exactly like Celty with her head on. Can we say, yikes?
** And then, after it's revealed that Mika is in fact Seiji's stalker and not a human body with a different head attached to it, they stay together [[spoiler: even though Seiji keeps telling Mika that he's only staying with her because her face looks like the random head he found so many years ago, and that if he can be reunited with it, she's history]]. And she just eats this up for some reason.
* [[spoiler: Ran Izumii. He's threatened at least two women with rape, and it's heavily implied he raped his little brother, Aoba.]]
* Mika thinking to herself about how she wants to crush that head and eat its blood so then Seiji will love her. Also, she's bugged everyone and knows everyone's secrets, even more than Izaya himself. [[ParanoiaFuel This girl knows everything you're doing at every moment. She knows you secretly started a gang over the internet, she knows you disbanded a gang and don't want anyone to know. And she does this just so she can make sure there are no enemies for Seiji.]]
** If going by the anime, ''Seiji himself knows this.'' And he's ''totally okay with it, too.'' On the upside, it does seem to imply that their relationship is a genuinely happy one. Or that Seiji has StockholmSyndrome.
* A young Namie taking showers with Seiji is sickening. Her incestuous love for him is horrifying. We're talking about his own SISTER, who grew up taking care of him, and she actually wants to shatter his trust in her by making babies with him. Talk about mentally scarring stuff here....
* Anri. She's emotionless because there's this crazy weapon in her head, telling her to cut everyone she meets. [[FridgeHorror How often does that voice tell her to cut Kida and Mikado and cut everyone else she meets?]]
* Shinra and Mikado's beatdowns at the hands of the stalker. Especially the sounds Mikado makes as his head is slammed against the wall. These scenes also double as a TearJerker.