Nightmare Fuel / Pokémon: Rise of the Rockets

• The Lavender Town Hypno. A pair of Hypno driven insane by... something. What actually happened to them has never been fully elaborated upon. The plot itself was inspired by the infamous Hypno's Lullaby, as well as the inherent creepiness of Hypno's lore.
• The Unown, in general.
  • They effectively killed everyone in Azalea Town in their first appearance, and only barely managed to be contained by Ethan and Quincy before they destroyed everything else.
  • Those in the Sevii Islands enacted untold amounts of Mind Rape on Alexa, a young girl, and came very close to killing Colette and Jayron.
• Kyle's mental confrontations with Keston Ail—as well as Ail's sheer, unnerving and unnatural existence for Kyle—could be seen as this, given how hopeless Kyle had become by that point.
• The Ancient Darkrai are this in spades. From their total disregard for human life, to the pleasure they take in putting people and Pokémon everywhere to sleep and inflicting the worst nightmares possible on them. Not to mention that their sheer power meant that Arceus couldn't even directly destroy them, instead being forced to imprison them for millennia just to weaken them for later.
  • Those same nightmares have been shown to have lasting impacts on many of the people affected by them.
• Ford's callousness and willingness to kill virtually anyone as a means to his ends can be extremely unnerving. Similarly with his Agents.
  • Not to mention, when the Sevii Islands Unown were asked why they were acting the way they were? Their only response was "Ford."
• And speaking of Mind Rape—what was the Hojohsin League doing to Levi when he first joined them?
• The Seven Deadly Sins are full of Nightmare Fuel.
  • Sloth effectively wiping the floor with Nine.
  • Wrath's first appearance and the fact that all of the Legendary Pokémon nearby went berserk immediately after he arrived.
  • Envy's first appearance, in which she went berserk and atomized almost all of Team Galactic—after manipulating Mars into shooting Saturn dead.
  • James Arthur and Meghan Vert being trapped in the same room as Lust and Greed, with no way to contact the outside for help.
  • Gluttony fully succumbing to his corruption, which also served as a Tear Jerker. More than that, there's no reason to believe that the other Sins did not experience similar Mind Rape when they were corrupted.
  • Pride's Aura was described as "incomprehensible" when Aria tried to read it. There's no clearer demonstration of just how messed up the Sins are than that. Not to mention how quickly Pride can shift from being calm and collected and into Suddenly Shouting.
• Ellen's gradual Break the Cutie plot, having witnessed first-hand the destruction of much of Unova, the power of the Ancients, the destruction of Sootopolis, and much more.
• The attack on Havoc.
  • Quincy almost seems to have jumped off the deep-end by the time she starts it—except not, as she's shown to still be perfectly in control. Her Dissonant Serenity while hunting Michael Travis is... eerie, to say the least.
  • The sheer brutality of Déoza's agents, and that of the brainwashed Team Energon agents, all of whom listlessly mow down whatever Team Magma agents they come across all while giving no regard for their own safety.
  • By the time Team Liberty and Team Rocket forces arrive to assist Team Magma, the entire place is just... empty. Devoid of life—filled only with the dead and dying. The sheer silence they encounter really sells it, and understandably horrifies some of those involved, such as Skye.
  • The fates of Vasilyev, Stiles, and Abbing at Quincy's hands. Even though they were new characters, they received quite a bit of development and were some of the only Team Energon NPCs to get real personalities and act like real people. To see them all killed so mindlessly... Especially since Ryan H. could only watch as they were killed, one by one.
    • Abbing pulls a Heroic Sacrifice to save Vasilyev from a cloud of psyhically-controlled shrapnel, pushing her out of the way and winding up shredded herself in the process.
    • Abbing's death enrages Stiles, prompting him to attack Quincy with his Pangoro. Both wind up frozen and broken by Ent, her Abomasnow.
    • Finally, Vasilyev suffers an extreme Heroic BSoD, and can do little to help her subordinates until it's too late. By the time she recovers and can fight back, she's trapped with Michael Travis and Maxie in a metal pod and dropped into the volcano outside.
• The Train Episode. Just what the hell were those creatures?