- The execution scene in the first episode. Doesn't help we can see the doomed man's tears soaking through his hood. The crowd shouting "KILL! KILL! KILL!" is also distressing, as their outrage at an unrepentant murderer being released wasn't enough to stop their bloodlust.
- At the end of episode 15, the Count sends Albert back to Earth and then he cries, knowing what he had done to Albert. But when they show close-ups of his face, only half of it is sad, the other half is the evil Gankutsuou smile. Now that by itself is creepy, but when the Gankutsuou side takes over, the cries immediately transform into the freakiest evil laugh ever heard. Joji Nakata provides a knock-out performance and the animation supports the moment brilliantly.
- Andrea Cavalcanti at first seems like an effortlessly charming Bishōnen but is eventually revealed to be outright deranged to the point of seducing his mother and almost raping (or does he really?) his half sister and stabbing his father. And let's not forget Danglar's Death by Materialism, preceded by a good amount of madness...oh, and Fernand Mondego, who snaps to the point of shooting his wife and son. Or Héloise de Villefort and her masturbation scene and the whole thing with her poison ring...
- Everything that involves Gankutsuou. Albert's nightmares about the Count (especially after he kills Franz). The execution scene (especially in the manga... ohmygod). Edmond's imprisonment. Haydee's whole past. Your mentor and substitute father stalking you and trying to kill you. Your dad turning out to be a parvenu and an opportunistic betrayer and murderer, then trying to kill you along with your mom, then trying to kill a young girl whose father he already murdered. Your future husband trying to rape you and turning out to be both a criminal and your half-brother. Phew, Someone's having a bad day.
- Andrea at one point attacks Haydee with a crazy look on his face and looked like he was gonna try to rape her but the Count shows up and he stops.
- As mentioned above, after Franz's death, Albert has a dream that ends in him killing Franz himself. But Franz doesn't just die; his entire body turns in a mass of blood, as does everything around him and Albert. Talk about a bad dream.
- The end of episode 19 where Andrea assaults Eugenie pinning her to the ground with the intent to rape, ripping her clothes off violently all the while laughing maniacally about how he will "ruin her". It's very distressing to watch.
Nightmare Fuel / Gankutsuou
For an alternate take on The Count of Monte Cristo, Gankutsuou has a few moments of pure Nightmare Fuel. Spoilers below.