Complete Monster/Inuyasha

File:Naraku.jpg
Many fiends, beasts, and demons inhabit the Feudal world of *Inuyasha*, but only a few stand out as thoroughly horrible.

* Naraku, the series' Big Bad, is a half demon who wishes to become a full demon by using the sacred Shikon Jewel. How does he want to go about doing this? By messing up the lives of every single one of the main cast's lives because he can. He was responsible for every major atrocity in the series: Miroku's Wind Tunnel curse, Sango's brother becoming Brainwashed and Crazy, reviving a group of serial killers to slaughter his enemies, and sending his minions to kill villagers to lure the protagonists to him. He's a mastermind at manipulating others to do his bidding and he's killed Kikyo numerous times because he wants to remove the only side of him that could possibly be redeemable. If that wasn't bad enough, he essentially was responsible for Kikyo and Inuyasha's falling out and killed a huge margin of Koga's wolf clan. He's also not above killing his minions if they choose to disobey him and killing innocents if they even so much as become inconvenient to him. He doesn't have any ties to any other person, human or demon. All you can do is try to kill him. But what he can do to you...And to think he was this bad BEFORE he was Naraku. Becoming Naraku just gave him the power to be as colossal a Jerkass as he ever wanted to be. Ultimately, he never even truly loved Kikyo: he just really wanted to have her as his own.
* Taigokumaru is a sick, twisted, sneering, arrogant, elderly Bat Daiyoukai with no regard for the lives of anybody. And, no, not even his family are exceptions to this. Proof? Before his appearance, he killed his son, Tsukuyomaru, for threatening to leave the Demon Bat tribe if he didn't leave the local human village alone (which he gloats about later, saying he took great pleasure in it) and threatened to destroy the humans if they didn't hand over his half-demon granddaughter Shiori, just to use her as a replacement for her deceased father to preserve the bat barrier. He does not keep his word, deciding to lead an assault on the village anyway and abusing Shiori as a source for the bat barrier, threatening to kill her human mother if she doesn't co-operate. While he calls his granddaughter 'precious' and says he wishes to keep her away from the humans who bullied her, it's not actually out of concern for her but part of an emotional manipulation tactic to get Shiori to side with him and maintain the bat barrier. Considering he killed his own son over a simple disagreement, it's safe to say he could just as easily do the same to Shiori, further supported by the fact that his spirit attempted to drag her into Hell with him. A thoroughly depraved being devoid of any affection, regret or empathy, Taigokumaru represents the arrogance, sadism and misanthropy of Daiyoukai at its absolute worst.
* The Spider Head Leader who pretends to be a kindly priest to Nazuna, under the pretense of protecting her from the Spider Heads under his control, and killed her parents all for the Sacred Jewel in Inuyasha's possession. Also he planned to eat her and subject her to a Fate Worse Than Death as Spider Heads are created from devoured victims.
* Gatenmaru despite part of his name meaning heavenly and wearing effeminate lipstick and a pink haori and his men are really nasty victims of their own hedonism. Gatenmaru, himself leads a band of blood thirsty bandits who pillaged and had them slaughter an entire village of a kind old man and his grandson who had Inuyasha and co had saved while masquerading as a human, and these men had done these evil deeds willingly even after discovering their boss was truly a demon, in fact became even more enthralled in their actions. Gatenmaru feeds off women quite literally, by eating them alive through draining their essence through his tongue while showing sadistic satisfaction in their deaths. He does all of this Forced to Watch while he had poisoned and captured Inuyasha who had to watch helplessly as Gatenmaru mocked his weakness, referring to him as a lowly half-breed. Safe to say, nobody was upset when he and his men are gruesomely ripped to shreds as Inuyasha's demon blood awakened out of the sheer anger at him.