Complete Monster/Super Sentai

Whenever Super Sentai decides to go Darker and Edgier, expect these kinds of creeps to appear. Of course, the Lighter and Softer ones might not be excluded from this...

Dengeki Sentai Changeman

 * Star King Bazoo is probably the Ur-Example for Super Sentai; he is a giant blue torso head with exposed organs who began his campaign of interstellar conquest and subjugation by destroying a planet of winged people so peaceful and kind that merely looking upon their smiling faces and hearing their voices will make you lose all violent impulses. All his forces are comprised of the champions of those worlds he'd already conquered, forcing them to fight for him lest he finish the absolute destruction of their homes. Not that he intends to ever let them go back, of course.

Hikari Sentai Maskman

 * Underground Emperor Zeba. Tube's dictator who has absolutely no compunction about killing or punishing his subordinates. His monstrosity is finally revealed in the final episodes where it turns out that he is

Kousoku Sentai Turboranger

 * Surprisingly, Ragorn looks less of a Complete Monster in comparison to Bouma Princess Jarmin. While she is nonetheless loyal to Ragorn, she has a really nasty thing in manipulating her allies' emotions. For instance, during an episode featuring an Ice-Fire Bouma siblings, the Ice Bouma reconsidered in not fighting the Turborangers out of concern for his brother. Jarmin's solution? Incite the Fire Bouma to try and kill off his brother. And once that's done, she combines them into one monster. Her biggest Moral Event Horizon, however, was against the Bell Chime Bouma, a female monster whose tribe was locked away by Jarmin herself inside a bell chime and threatened her into fighting the Turborangers; in this case, get Youhei/Blue Turbo mesmerized and alienated from the team or else the whole tribe is destroyed. Oh, and she still whips her when she's not seriously fighting. And when the Turborangers break the spell? There comes Jarmin, destroying the bell chime containing the whole tribe, in front of the Bouma herself, and kills her right after, THEN turn her into a giant monster for the Turborangers to fight. Yowch, nasty bitch. Jarmin herself being a Complete Monster is an accomplishment amongst female Sentai villains. Usually, in other Sentai series, villainesses are treated with sympathy or don't surpass the boys in terms of depravity (Shibolena, Venus, etc. come to mind). If they do, like Grandienne below, it's because of her position as the Big Bad. Jarmin was merely the Dark Chick, an underling, and yet she surpasses Ragorn in depravity.

Choujin Sentai Jetman

 * Back Dimensional Count Radiguet is without question the worst Complete Monster in Super Sentai history, Radiguet is a Sadistic Ax Crazy Genocidal maniac with megalomaniacal fantasies of ruling the Vyram under an iron fisted Dictatorship, When Juza his boss and the true Big Bad Arrived he planned to overthrow her but that failed when it looked like he would become good because of a sick girl who became his Morality Pet while he had amnesia whom he cured unknowingly he turned her offer to turn good by killing her and this was all because she believed he could feel love,he's also the one who for no other reason For the Evulz, his most repulsive Kick the Dog moment was when he killed her after she snapped back to being Rie, there's also the part where he tortured  Truly a vile piece of scum.

Gosei Sentai Dairanger

 * Colonel Shadam is a pretty nasty version. Responsible for many bad things in the series on top of the fact that he cares nothing for his two sons and wife, his amazingly abusive treatment to Akomaru is the ultimate proof of this. He shows zero honor at that: when Doushi Kaku showed mercy for him and the tables were turned for his side, Shadam instead uses the chance to mercilessly and brutally murder Kaku through utter Curb Stomp Battle. He also doesn't give one freaking shit about any of his subordinate, and the fact that  It's particularly cathartic when he met his demise...

Denji Sentai Megaranger

 * Commander Guirail. Unlike Noble Demon Yugande, who is honorable and dislikes underhanded tactics, Guirail has absolutely no qualms about doing whatever he feels is necessary to win. His first appearance even has him using CHILDREN as human shields. He also has no loyalty to anyone and is willing to hurt or possibly kill his comrades. Ultimately, when Guirail severely injures Yugande by using him as a Human Shield against the Megarangers, Hinelar decides to end it by offering Guirail a Psycho Serum in the guise of a power-up to turn Guirail into a mindless One-Winged Angel. Guirail is soon the first to be killed by the Megarangers' Mid Season Upgrade mecha. Seeing him writhing in agony due to the serum before getting killed by the Megarangers is quite satisfying.

Rescue Sentai Go Go Five

 * Grand Witch Grandienne, who deliberately sent her children out to die, brainwashed one to kill another on several occasions, banished one to Hell, and resurrected two of them as brainwashed zombies. As fitting of the family theme in GoGoFive, Grandienne stands for everything the Tatsumi family bond isn't.

Mirai Sentai Timeranger

 * Captain Ryuya, Tatsuya Asami's Identical Grandson (give or take a few dozen 'greats'), was the ultimate mastermind behind everything that occurred in the series -- from the initial escape of Don Dolneiro to Gien's insanity. In other words, he was responsible for the crisis that took place in the finale . The worst part is why he manipulated everything that happened --.

Tokusou Sentai Dekaranger

 * Agent Abrellar, who'd sell lots of weapons supporting galaxy-destroying wars for profit and fun to most of the Alienizers, regardless of how many lives were taken. One galaxy destroyed, he moves to another galaxy to generate profit and destruction.
 * Oh, it's even worse for Abrella: most of the Alienizers have some sort of twisted logic to justify their actions and are shown to have some modicum of standards to their deeds. Aburella, however, treats any and all crime as a business opportunity, and it doesn't matter if you're destroying entire cities, selling slaves, pawning stolen merchandise, or filming child pornography, as long as the price is right, he'll be more than happy to sell you the tools you need to further your enterprise. And his Villainous Breakdown near the end of the series? All caused merely because the Dekarangers were ruining his transactions. Yes, Aburella himself caused a citywide destruction spree and nearly destroyed the whole of the Space Police simply so he could keep his job. He and Pigma would get along just fine...

Mahou Sentai Magiranger

 * Mahou Sentai Magiranger's Absolute God N Ma is a dark being described as being made of nightmares and hunger. Even when reduced to a giant eye in a window, he still wields undeniable authority over his minions, and once he does emerge... Oh, and there's also the part where he forcibly brainwashed Magitopia's greatest hero into becoming his most loyal servant.
 * Then there's his minion, the Hades God Cyclops. After a brief skirmish with the Magirangers, he vanishes and begins firing upon them from multiple directions at once, deliberately stringing them along into thinking they've figured out how to escape his bullets, only to take one of them down. When he takes down Urara, Tsubasa experiences a total nervous breakdown, and Cyclops simply exclaims that there's no greater pleasure than watching someone's mind break.

Juken Sentai Gekiranger

 * Long the Immortal Dragon. His motives boiled down to "I'm Immortal. Bored. Now, let's destroy the world for fun!". Just about every bad thing that happened in the Gekiranger world (the formation of Kenma, as well as the death of Rio's family and setting him up to fall to the dark side) can be traced back to Long's action to relieve his boredom, which includes the death and suffering of humanity, but Long gives no damn at all, for he thinks that he's an ancient being that has 'guided' humanity, and thus has the right to screw them over in any way he wants.

Samurai Sentai Shinkenger

 * Sujigarano Akumaro was sinister, even for the Gedoushu. His ultimate plan was to cause sufficient suffering to drive wedges of said suffering into six precise locations, as part of a ritual to open the way to Hell so that he could taste absolute human suffering -- even though this ritual would destroy both the human world and the Sanzu River. Also, he made Fuwa Juzo's sword from Juzo's dead parents, whom he murdered himself. His monstrosity extends to even his Ayakashi, who seem specifically made to cause as much suffering as possible to further his goal.
 * Fuwa Juzo was a remorseless Blood Knight to the point that even his fellow Gedoushu didn't trust him; he even only became a Gedoushu in the first place so that he could keep killing in spite of his sickness. Akumaro saw potential in him for his ability to walk the line between humanity and the Gedoushu and sought to use him to open the gates of Hell. However, he throws a sharp wrench into the plan, declaring that he already knew that his sword made by Akumaro was made of his parents, and, moreover, he didn't care.

Tensou Sentai Goseiger

 * Bruajira of The Messiah, a Manipulative Bastard of the first order, he manipulated four seperate villain factions. Warstar, Yummaju, Matrinis and and stabbed them all in the back like The Starscream that this slimeball son of a bitch was that this SOB is, his revealed backstory proves what a Complete Monster he is when it's revealed that  For those of you who don't know what that is his main goal was to destroy the earth and rebuild it in his image making those who survived worship him just to feed his God Complex. Also in the finale when he's defeated by The Gosiegers he promises to take Earth with him although

Kaizoku Sentai Gokaiger

 * It's hard to get a Complete Monster when your boss (Warz Gill) is a General Failure, and his replacement/dad (Ackdos Gill) just sits down on his throne and give out normal orders like how every other normal Sentai villains behaved. However...Basco ta Jolokia fits right in, representing greed and It's All About Me to the max. The guy betrayed the Red Pirates, leaving Aka Red to his apparent demise and Marvelous alone, while stealing several of their gathered treasures under the pretense that 'you have to sacrifice something to get something else', which means that if he wants something, he sacrifices ANYTHING to get it and isn't above blackmail. Children will be hurt, schools and youngsters will be blown up, allies will be betrayed (including the Morality Pet) for anything he wants. The cinch? He does all that with a cheery smile befitting of a Troll and did it for profit and whatever fun he wants. It's worth noting that Basco's disposition is usually cheery and jovial, but when he is the enemy of the week, the situation gets even worse than when Zangyack is the enemy of the week.

Tokumei Sentai Gobusters

 * As early as 10 episodes in, Enter gleefully entered this position. Starting from his 'attempts' to appease his Majesty Messiah, which involves causing misery as much as he likes and pulling Unwilling Roboticisation, even on children, using them as human shields in much more frequently than Guirail could even muster and, on top of that, having a blast while doing them with an unabashedly relaxed, but still nasty speech pattern peppered with French phrases. He's like a Basco that has been around ever since the first episode. Even after Messiah is apparently destroyed, he seems to escalate his horrors, going so far as to implant himself with two cards containing backups of Messiah's data—one of which also contains Masato Jin's data— in order to become the new Messiah, as well as implant Hiromu with another card to serve as his Soul Jar, forcing the Go-Busters to face the possibility of killing Hiromu in order to stop Messiah once and for all. He even threatens to harm Hiromu so grievously as to put him into a coma, just so that he can keep his Soul Jar alive without worrying about Hiromu attempting to off himself—assuming the card would let him do so.

Unsorted

 * Other truly monstrous Sentai villains are Great Emperor Ra Deus, Dezumozorlya, and Prime Minister Yogoshimacritein.
 * Some of the Big Bads' minions aren't far behind when it comes to their despicability. Examples include Great Doctor Lee Keflen.