Nightmare Fuel: Death Note

It goes without saying, Death Note is a rather terrifying universe and here are the myriad of examples that support it.
General
  • The Death Note itself. That notebook could have ended up in the hands of anyone, anywhere.
  • Light Yagami. Or, rather more accurately, what Light Yagami becomes. He starts out as an innocent idealist (as seen in the Yotsuba Arc) and slowly becomes more and more ruthless, horrifying and generally evil, until he's reached the point where he's only barely recognisable as the same person he was.
  • Basically every time Light goes into crazy Kira mode, with the maniacal laugh and the red eyes.
  • Light and Misa in and of themselves... they're adorable... (in some of the early manga artwork Light kind of looks like a Disney character) and well, you know...
  • L may have looked a bit creepy with his big, baggy eyes... but Mello took this Up to Eleven.
  • Ryuk can be this. Especially during the earlier chapters, when he's there to provide Exposition on the nature of Death Notes and Shinigami. Those eyes...
  • Teru Mikami — or, how an otherwise decent person can go completely off the deep end. The part where he spins around in his chair and laughs is the worst. Good choice, Light.
  • The anime's second Title Sequence. It's pure chaos. The entire sequence is nothing but dark and twisted imagery bathed in harsh colors, (for example, a screen covered with laughing, demented Light faces). The opening song, Maximum The Hormone's "What's Up, People?!", only adds to the disturbing atmosphere, with lyrics such as "Hey! Hey! A hymn to humanity/Love has gone, People, are you worried?".

Light/L Arc
  • In the very first episode, Light locks himself into his darkened bedroom, pulls out his Death Note, opens it up to reveal all the pages and pages of names of the people he's killed, smiles down at it, and then breaks out into creepy, creepy laughter.
  • Light's voice whenever he details one of his plans. For example, the way he looks down at the dying Raye and says "Goodbye, Raye Penbar." in that mocking tone.
  • Naomi's death, particularly if you hold to the theory that people under the control of the Death Note are still capable of thinking independently, effectively rendering them prisoner to their own bodies. If that is true, she walked to her own suicide completely against her own will and could do nothing to stop it.
  • The Yagami family. Sayu has a brother who's perfectly willing to kill her if he thinks she's getting too close to uncovering the truth. Light even suggests, early in the series, that he's willing to write down his junior-high-school aged sister's name in the notebook if she so much as sees it.
  • Misa in custody. Imagine the mental state of the poor girl. She's taken off the street, continuously blindfolded and restrained for two months, under constant surveillance, and she has no idea why she's there or if she'll ever be untied.

Yotsuba Arc
  • L's death. The poor guy suddenly collapses from a heart attack by Rem's doing and the last thing he sees before he dies is Light staring at him while giving him a huge Slasher Smile.
  • The moment Light moves from saying "I'm going to create a perfect world" to "I've gotten rid of everything in my way." This shows he's Jumped Off The Slippery Slope into true evil and has absolutely no chance of redemption from here on out.
  • Higuchi's absolutely horrifying Slasher Smile. Rem, a Shinigami, is noticeably freaked out by it.
  • Misa Amane wears an Elegant Gothic Lolita style dress in one instance, for when she was committing suicide after she thought Light died. Overall, the dress combined with her depressed facial expression and her dark make-up makes her look like a life-sized porcelain doll, to an eerie effect. That scene mirrors an earlier scene where Misa, dressed the same and traveling through the same setting, sings a capella about her devotion and trust to Kira. Though the lyrics are optimistic, her tone, and doll-like dress, makes the scene still quite creepy.

Mello/Near Arc
  • Light's death. In the manga, it's even worse. you see his dead face on a two-page panel, with a horrifying expression, which is worst upside-down.
    Light: NO! STOP IT! I'M GOING TO DIE! I DON'T WANT TO DIE! I DON'T WANT TO DIE! I DON'T WANT TO GO...
  • The revelation of the Death Note's last rule: "All humans, without exception, will eventually die," and, "When they die, the place they go is Mu (Nothingness)." Especially in the anime, where Light is moments away from his horrific demise and the scene simply cuts to the rules, with no music but one rather ominous church bell funeral toll. The overall effect is damn chilling.
  • Light and Mikami's facial expressions in the last two episodes. They look absolutely demented.
  • The scene where Mikami is introduced. He intervenes in a debate on TV about Kira by slaughtering the audience in various gruesome ways. One of them gets his neck twisted in 180 degrees.
  • What Misa Amane and Kiyomi Takada end up becoming — two women completely devoted to a manipulative sociopath and willing to kill for him.
  • Takada's fate. She ends up being burned to death by Light. And this was after her getting kidnapped and forced to strip in front of Mello. She could not have been in a more terrifying position. At least she seems to be unconscious when she dies.

Other
  • At the end of the first relight, the unknown Shinigami heads off to the human world to repeat the cycle, meaning that everything that just happened, will happen again.
  • Some scenes from the second Rewrite (L's succesors):
    • There's an altered version of the scene where several SPK members get killed, except this time by Mikami instead of Mello. Here they put some really Uncanny-Valley-ish expressions. And one attempts to kill Near with his gun. The final shot shows Near staring silently to the screen, covered by the blood of the corpse that's right next to him.
  • Beyond Birthday; there's a reason he's on the quote page for Cruel and Unusual Death. From the first paragraph of Another Note:
    When Beyond Birthday committed his third murder, he attempted an experiment. Namely, to see if it were possible for a human being to die of internal hemorrhaging without rupturing any organs. Specifically, he drugged his victim so they fell unconscious, tied them up, and proceeded to beat their left arm thoroughly, being careful not to break the skin. He was hoping to bring about enough hemorrhaging to cause death from loss of blood, but this attempt ended, sadly, in failure. Blood congested in the arm and it turned purplish red beneath the skin, but the victim did not die. He simply shook, convulsed, and remained alive. He had been convinced the blood loss incurred was enough to kill someone, but apparently he had underestimated the matter. As far as Beyond Birthday was concerned, the actual method of murder rated fairly low on the amusement scale, and it was never more than an interesting experiment. It did not particularly matter to him whether it succeeded or not. Beyond Birthday simply shrugged, and took out a knife...
  • From the Pilot chapter, Taro's nightmare. The people he accidentally killed return as reanimated corpses to accuse him and grab at him with their skeletal hands.