Complete Monster/Naruto

The world of Naruto has plenty of villainous characters, and some of them manage to be in a league of their own...

Manga, anime and movies

 * Haido, Big Bad of the second film, was seemingly a friendly Well-Intentioned Extremist who wanted to create a utopia. However this was just a facade, as his true goal was to find the legendary Stone of Gelel and use its mystic power to Take Over the World. He attacked Temujin's village and had everyone slaughtered save for Temujin himself, whom he made his servant. When Temujin does find out it was Haido who murdered his parents, his former master simply mocked him for being blind and in the dark for so long. To make matters worse, he turned many of his servants, including Temujin's friends, into mindless armored soldiers to follow his every order, many of whom were also children from villages he attacked. In the climax, he forcibly removes a piece of the stone from Temujin's body that he gave him, rendering the boy weakened and proceeds to beat him and Naruto to near-death. A power-hungry and manipulative sociopath, Haido cemented himself as one of Naruto Uzumaki's most depraved adversaries.
 * Anime-only Filler Villain he may be, but Shiranami of the Tsuchigumo clan is one seriously nasty piece of work. He murdered his own father in an attempt to obtain the Dangerous Forbidden Technique which his father had been protecting just for the money it could get him, nonchalantly enslaved an entire village, pretended to sympathize with Hotaru's (the container of the forbidden jutsu) loneliness, and offered to help her restore their clan before revealing that he doesn't care about Hotaru or the clan at all, forcibly activated the forbidden jutsu inside the poor girl (which she had been trying to get rid of, but he manipulated her into keeping it) and considered her a mere "tool" that he wants to use to "steal the world" for himself. He cheerfully describes the act of killing his father to Hotaru and tells Naruto and Utakata that the main reason he killed him is simply because he's greedy. Nonetheless, Shiranami thinks that, compared to Utakata, who doesn't care about his own village either but still cares about Hotaru, he's a "pretty fine" person. He admits that they don't need to worry about Hotaru because she will live on with him in the world he hopes to create, but she will spend the rest of her life as his "tool/weapon" with no free will of her own. Oh, and episode 150 ends with him forcing the forbidden jutsu activated!Hotaru to fight Naruto and Utakata against her will. He then tries to murder everyone who'd try to prevent him from accomplishing his insane goal.
 * Another Filler Villain who qualifies is Kazuma of the Land of Fire. A former friend and comrade of Asuma Sarutobi and Chiruku, he saw the Hokage, and by extension the entire Konoha village, as a threat to the figurehead Fire Daimyo. Originally, he convinced half of his comrades to try to assassinate the Hokage while Asuma stopped him, and seemingly killed him. Years later, after it was revealed he implanted Kurama's chakra into his son Sora to create a weapon to destroy Konoha, he attacks dozens of border towns with his men. After killing thousands of people, he raided the tombs of his former comrades and would use them to make a Weapon of Mass Destruction to incinerate every man, woman and child in Konoha, all the while constantly beating Sora and manipulating him into turning on his new friends. The people he killed on the border towns were used to create a small-scale Zombie Apocalypse around Konoha to distract, and trap, everyone in the village. Finally, when that plan failed, he triggered his son's Super-Powered Evil Side and sent him to destroy Konoha. As he died at Asuma's hand, Kazuma's last thoughts were of how the Land of Fire could do without him.
 * There's another Filler Villain named Disonasu. He seems to be the kind leader of Hachō Village. In truth, he is a Serial Killer who once collaborated with Orochimaru on reanimation. Desiring power after a defeat at the hands of Pain, Disonasu teams up with Kabuto in order to acquire the ancient device known as the Ama no Hoko, ordering and participating in a massacre on the nearby Tonika Village to gain the "Sounds" necessary to activate it. When he finds two of the Sounds missing, Disonasu orders Kabuto to attack his own village to find them, resulting in a battle that nearly destroys the whole town in the process. In spite of being aware of the world-destroying power of the Ama no Hoko, Disonasu activates it anyway for the simple reason of wanting to regain the power that he lost long ago.
 * Out of all the Akatsuki's members, Hidan is the worst of the bunch. He has no sympathetic backstory, no Freudian Excuse... nothing. He's simply a perverted, serial-killing maniac who revels in the bloodshed that he causes. A foul-mouthed, murder-obsessed sicko hailing from the village of Yugakure, Hidan hated the natives of the village for their peaceful ways and slaughtered his neighbors before ditching the village. He soon began to worship Jashin, the god of murder, bloodshed and depravity, and murders in the name of his religion. The first time he's seen as an Akatsuki member, he and his partner Kakuzu corner the host of the Two-Tailed Beast and and deliver her to their boss Pain so she can have the beast forcibly extracted from her, killing her in the process. He then goes on to attack a temple and slaughters every monk inside, never mind the fact that he only needed to kill one of them. However, what he does to is easily the worst act he commits: he initiates a religious ritual that binds his soul to 's, and proceeds to slowly torture him to death through self-mutilation. This is Hidan's favorite way of killing people, and thankfully the sick bastard gets his when he tries to inflict this fate upon Shikamaru, only to end up decapitated and buried alive, unable to die due to his immortality.
 * And then there's the series' ultimate Big Bad, Madara Uchiha, who plans to destroy the entire world so that he can control all that remains. He uses the excuse that he wants to make a world where there is no more struggling and everyone is equal, but delving into his backstory and motives makes it pretty clear that he truly just wants to be God amongst all other men because he's a Sore Loser. He cursed his entire clan as well.

Boruto

 * Momoshiki Ōtsutsuki, the main antagonist of the Boruto movie and True Final Boss of the series, not only matches them all in heinous crimes... but has zero Freudian Excuses, being a power-hungry madman who truly believes that hard work is for losers, preferring to absorb and steal other people's powers instead. Momoshiki and his partner Kinshiki set out to accomplish where left off and recollect all chakra in order to create a new chakra fruit to become all-powerful. Invading Earth for this reason, they attacked and absorbed Killer Bee's chakra, nearly killing him in the process. They then made their way to Konoha's Chunin Exams, causing wanton destruction to the place in an attempt to kill Naruto, Sasuke and their children. At one point, Momoshiki even launched an attack powerful enough to destroy the entire Fire Country, Laughing Mad about innocents dying in the process. He later takes Naruto to his dimension and tries to absorb Kurama's chakra clean from him until he dies, and when the other Kages show up to stop him, he decides to absorb Kinshiki in order to kill them all, forcing a near-dead Naruto to watch. To top it off, when Boruto uses a Rasengan to free them all, Momoshiki is enraged at his garments being damaged and attempts to brutally murder Boruto just for that.
 * Isshiki Ōtsutsuki came to Earth intending to create a new God Tree in order to unleash his full power and wipe out humanity. After being betrayed by, Isshiki hijacked the body of a young monk named Jigen, keeping him as a prisoner in his own mind for a thousand years as he formed Kara. Being responsible for the deaths and experiments of Kara, including the horrific deaths of almost all of his prospective vessels, Isshiki later emerges to try and take over Kawaki's body, planning to restart the God Tree's creation. After Jigen's body is destroyed, Isshiki becomes a malevolent Spirit Advisor to Code, the sixth member of Kara's inner circle, telling him to continue his plans and exact revenge on Jigen's killers.
 * Victor, the fifth member of Kara's inner circle, poses as a seemingly genial businessman so he can cultivate a new God Tree in order to achieve eternal life. Having his own researchers experimented on and murdered, Victor later cultivates the incomplete God Tree with an attempt to feed all of his company's workers to it so it may bloom its Chakra Fruit, intending to unleash it on the Land of Valleys in an attempt to prolong his life.
 * Deepa, the seventh member of Kara's inner circle, is involved in the cultivation of the God Tree's fruit, intending to help Victor unleash it so he may taste it and then run rampant along the world, killing as he goes. A sadistic killer, Deepa is introduced having massacred everyone in a restaurant before killing everyone in his way of getting to the stolen Hashirama Cell that Victor also seeks. Later massacring another restaurant, something entirely routine for him, Deepa is shown to have no hesitation attempting to murder children or anyone who even mildly inconveniences him, all to savor the "flavors" of despair.

Other material

 * The Light Novel Konoha Shinden: Steam Ninja Scrolls: The Jashinist Ryūki poses as a holy man seeking to help people connect to their loved ones. Behind a series of kidnappings while seducing young women into his sect, Ryūki brings them for a holy ritual, though he intends to poison and offer them as blood sacrifices in a large number to his god Jashin in order to achieve immortality. Despising the peaceful era he exists in, Ryūki gleefully intends to throw the world back to chaos and slaughter, viewing the depraved Jashinist murderer Hidan as the only being worth emulating.
 * The video game Path of the Ninja 2: Genshō Ryūdōin, alongside his Co-Dragons and brothers Jakō and Rokkaku, attacked and destroyed a village in the Valley of Evil in order to unseal the Spirit Beast, a giant catfish-like demon with enormous power. Genshō plans to use the Beast to destroy worthless nations and their peoples so he could rule the world. Unsealing the Beast also unleashed its evil spirits, which can make a person aggressive and obsessed with attacking other people until their deaths. When Jakō tells him the evil spirits will reach Konoha before the Beast is fully revived, Genshō gleefully replies that he can't wait for that to happens. The evil spirits eventually reached the Hidden Sand Village and Konoha, corrupting their inhabitants. After Genshō absorbed the power of the Beast, he thanks Jakō for buying him some time by killing him. He then forces Naruto to watch him kill his friends by slowly draining their strength.