Naraku

I'm pretty sure this is from the scene where he sees the somewhat resurrected version of Kikyo for the first time. Since he was the one who originally killed her, that's quite a shock, but good villains have to be adaptable.

It's hard to overpraise the brilliant way Inuyasha's writers portray Naraku. Most villains -- anime or not -- are somehow comprehensible and forgiveable. They shy away from really atrocious deeds. They want to take over countries or planets and have inhabitants left to rule. Even Darth Vader did what he thought was best for the Empire.

Naraku is a true nihilist, out for himself only. He wants to use the Shikon No Tama to become a full youkai, since he is part human (a nice symmetry with Inuyasha, who thinks he wants the same thing). Unlike most villains he's a thinker and a planner, never needlessly exposing his true self to danger. He's totally ruthless: he's willing to kill as many beings -- even his own allies -- as it takes to get what he wants. During the series he's indirectly or directly responsible for the deaths of hundreds of hapless villagers and thousands of youkai.

One of his favorite techniques is to trick good-hearted characters into killing or betraying each other just to generate evil energy to desecrate the Shikon No Tama. Later in the series he builds up enough power to split off parts of himself that become powerful villains in their own right.

I could go on and on, but one last example of Naraku's imaginative cruelty: at one point he brings Sango's dead brother Kohaku back to a semblance of life and then uses the boy to torment her, forcing her to choose between killing her own brother and allowing him to go on causing death and suffering as Naraku's pawn.