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Nightmare Fuel: Sengoku BASARA
Oichi in the third game. She looks like a pale, emotionless ghost woman that drifts around the battlefield like a broken puppet singing creepy lullabies. Her weapon? Huge hands made of utter darkness (sometimes with nails driven through them) that can claw, crush and grab enemy soldiers, smashing them into the ground or dragging them down to hell itself. And her strongest attack summons a shadow being that carries her around sucking the life out of anyone in its path. Dulcis in fundo, her victory pose consists in her lying on the ground and playing with said demonic arms before they engulf her in blackness.
On the other end of the spectrum there's the eerie sobbing noises she sometimes makes for no reason, or the way every time an attack misses her she'll suddenly whisper "Kill me!"
At the beginning of any stage in which an opponent runs away (like Yoshihiro or Haruhisa) she turns it into a very creepy game of hide and seek.
"Ready or not, here I come. Now where oh where could you be?"
Mitsunari Ishida's constant death threats and vows of vengance against Ieyasu Tokugawa are very intimidating and unnerving. There is also the scene when Mitsunari discovers that Kanbe Kuroda has taken over Hideyoshi Toyotomi's castle. Yes, the castle of Mitsunari's lord. When Mitsunari finally encounters Kanbe, he gives Kanbe such a scathing diatribe that his pupils dilate and turn red. There are also his move "Reverence" where Mitsunari is overtaken by rage and dark energy, and his fighting style changes from quick and graceful to violent and bestial.
The Incident at Honnoji stage, where you fight a demonic Oda Nobunaga, is extremely unnerving the first time you go through it. Starts normally, with you running forth, fighting enemies, and trying to unlock a door by defeating a camp commander... only to be interrupted when all the enemies collapse in pain, dissolve in red energy, and vanish. Then you run around to five other camps, trying to keep this from happening, because as your officers note, Nobunaga is eating the souls of his soldiers. And if you're too late to beat a camp commander, the entire area erupts and kills all the enemies. And the kicker? Every time that happens, that's one more timeyou have to kill Nobunaga.
The sheer thoughts that must go through Matsunaga Hisahide's mind as he calmly strolls about the country, psychologically crushing people and then setting them on fire for kicks, are enough to make one shudder.
Not to mention absolutely everything he does in Utage. From killing Kojuro and Sasuke in front of Yukimura and Masamune, to stealing Mitsuhide's very name and identity... nothing seems too terrible for him to do just in the name of his own amusement.