Complete Monster/One Piece

""For Nami, continuing to draw maps here is the ultimate happiness! It's to fuel my ambitions! Once she's revealed the entire world with her maps, the Fishmen will have no more enemies and the whole world will become my empire! Can you think of any better way to use her? So I will make her draw maps in this room forever if I have to! After all, we're Nakama!" - Arlong demonstrating that he does not know the first thing about what it means to be Nakama." While many of the baddies from One Piece, like Don Krieg, Crocodile, Eneru, and Blackbeard walk the range from insensitive jerks to all out line-crossing assholes, there are a few villains who believe that the above characters just weren't evil enough:

Canon (Anime and Manga)

 * While the first couple of One Piece villains were simply obnoxious assholes whose most heinous deeds were committed when provoked, early villain Captain Kuro was the first of many true monsters in the franchise. While first appearing as the snooty but well meaning butler serving a kind-hearted woman named Kaya, Kuro was secretly a retired pirate captain who had grown sick of running from the law and was hatching a plan to raze the island he was hiding out on to the ground in order to obtain a large sum of money, most of it from Kaya's inheritance. He had his old crew of Black Cat pirates hiding in wait ready to invade the town and assault it while Kuro would attempt to hypnotize Kaya to leave him as the one to inherit her fortune before executing her. He didn't even NEED to kill Kaya, but he wanted to in order to have peace of mind, since he had always hated Kaya and thought catering to her whims to be degrading. Since he'd been acting as a father figure and friend to Kaya for years, this is truly despicable and heartless, and incredibly hurtful to Kaya when she gets told it by the man himself. He also attempted to wipe out his own crew in order to keep up the charade of Kuro dying a long time ago, showing that he was enough of a scumbag to view his own allies as disposable pawns, a view which seriously pissed off Monkey D. Luffy who holds camaraderie and friendship in high regard. It's hilariously fitting that Kuro's fate after the subsequent beat-down by Luffy was to end up forced back into the role of a pirate captain, on the run for the rest of his life with Marines and Bounty Hunters in hot pursuit.
 * The method Kuro used in order to fake his death before taking on the Klahadore persona already showed how little he valued his crew member's lives: he had his first mate Jango hypnotize a crewmate of theirs in order to brainwash him into believing that he was Captain Kuro and left him to be executed so Kuro could save his own skin. While Alvida, Morgan, and to an extent Buggy were quite dickish to their henchmen (Morgan executing a marine who wouldn't kill a small child being the worst of the bunch), Kuro is the kind of guy who will happily slaughter you even if you are a loyal pirate as long as it would benefit him.


 * Shiliew/Shiryu of the Rain, the bloodthirsty former Head Jailer of Impel Down counts. Completely Ax Crazy, he murdered dozens, if not hundreds of prisoners for fun, claiming them to be "just trash" and disgusted the current Head Jailer so badly that he had him arrested and locked in the prison's lowest level. When freed as a last resort to stop a mass-breakout, he cuts down his former workmates with no regard for them and sides with Blackbeard, but thinks of betraying him if he does not succeed in stealing Whitebeard's power. It's clear he has no empathy and loyalty for anyone but himself.
 * Admiral Akainu, real name Sakazuki, is a wonderful example of a Knight Templar who crosses the barrier between Well-Intentioned Extremist and Complete Monster. He debuts while crossing the Moral Event Horizon: he orders his subordinates to blow up a ship of evacuees that the Marines had promised to spare. His justification was that he thought that if there were any survivors from Ohara that the world would be in grave danger, although there's no proof that survivors of Ohara actually present any danger. Later in life, he brutally murders anyone who tries to flee from the battle at Marineford with his horrifying magma powers despite the fact that they'd make absolutely no difference in that fight other than serve as cannon-fodder for Whitebeard and his allies. Then there's what he does to Coby: The kid is pretty much the Only Sane Man and calls out everyone for wasting tons of marines' lives for the sake of killing a handful of pirates. Akainu immediately tries to kill him - and they're theoretically on the same side! If not for Shanks... He moves the series into Darker and Edgier territory by causing the first major present-day story death. When Sengoku stepped down and Aokiji had to fight Akainu for the position, which Aokiji ultimately lost, he left the Marines rather than serve under him. The guy is that bad.
 * Hody Jones is the Captain of the New Fishman Pirates who takes Arlong's Fantastic Racism and turns it Up to Eleven. He's more brutal, more racist, more treacherous, and more cruel, but the kicker? He pulls a reversal on Arlong's sole Pet the Dog moment; whereas Arlong was mortified when Luffy used a Fishman as a human shield, Hodi actually uses a Fishman as a human shield against an attack. One of Arlong's former crew, Hatchi, stated that, while Arlong was a bastard through and through, he'd never hurt a Fishman no matter what. Hody, on the other hand, is known for killing any who talk to or know them. In fact, when he tries to take over Fishman Island, part of his plan is to execute all who had signed Queen Otohime's petition. This means that he's planning to murder thousands of its residents. He already killed Otohime and framed the human he hired to burn the petitions in the first place as part of this plan... and got cocky enough to brag about it in front of all Fishman Island.
 * Punk Hazard gives us the truly detestable Mad Scientist Caesar Clown. A Villain with Good Publicity who's convinced people he's a kind master and scientist who just wants to help people. The truth is that Caesar is violently jealous of his former associate Dr. Vegapunk and once took that frustration out by blowing up an island. In the present, Caesar keeps multiple children in his lab with promises to cure them of their sickness, and gives them candy to help them. The 'candy' is in truth an addictive drug to keep them enslaved to him, and his experiments will cause their deaths in five years. He shows no remorse, laughing he can always get more children! Caesar also saved pirates and sailors from death, but uses them as test subjects as well and turns them against their captain who was just trying to save them from him. When his back is against the wall, Caesar has no compunction killing these men with a poison gas he unleashes in an attempt to kill Luffy. His psychotic ego is rivaled only by his mile long sadistic streak.
 * Clown's boss is even worse if that's possible. Enter Donquioxte Doflamingo, one of the Seven Warlords of the sea, a former Celestial Dragon, and a flamboyant, gleefully violent lunatic of a man who rules over Dressrosa as its tyrannical king. Before the Dressrosa Arc it was very apparent that Doflamingo was not a good guy: Under the alias of Joker he participates in the slave trade by selling innocent people to the Celestial Dragons who are famous for treating their slaves like dirt, and he also works on the side as an arms dealer to Kaido, one of the Four Pirate Emperors by having Clown perform horrifically inhumane experiments involving lethal artificial Devil Fruits on innocent people (even children) that would inevitably kill them in pursuit of creating an army for Kaido. He also built up a reputation of a man not to be crossed by annihilating entire villages for petty reasons such as someone looking at him funny. But during the Dressrosa Arc is when he's shown at his worst: before the arc even began he approached its former ruler King Riku and blackmailed him into turning over the island kingdom to him for a large sum of money. Despite Riku being desperate to get his people to pool enough money together to pay Doflamingo, the bastard took control over him as well as his soldiers with his Devil Fruit powers and forced them to slaughter their own people before jumping in and "saving" the day after causing enough chaos and claiming the throne for himself. Under his rule the people of Dressrosa are transformed into toy slaves by one of his executives and are forced into labor, with their transformation's effects causing their loved ones to forget about them. When Luffy and Trafalgar Law form an alliance to overthrow Doflamingo, he responds by entrapping the city inside of a huge cage of strings dubbed the Birdcage which in time would slowly close in until it slices everyone inside to pieces as punishment for their defiance. And he's hardly exclusively horrible to people who oppose him: everyone close to him can find themselves victims to his wrath as well. He was willing to set up his own brother to die in an attempt to use his powers to grant himself immortality, tortures a fanatically loyal flunky of his named Bellamy for failing a mission and allows him another chance to prove himself only to have him killed anyway for being an eyesore, kills another loyal follower named Vergo by blowing up an area he was in, played off his executive Baby 5's dependence on love and affection to instill loyalty in her, and knows full and well that his henchmen will fall victim to The Birdcage and doesn't care in the slightest. He seems to treat members of his inner circle nicely, but as Law points out: he runs his so-called family on a foundation of ego and control and despite appearing to treat them nicely in return for their loyalty, he will happily toss them aside when he feels that he will get some sort of benefit from doing so, seeing them as disposable and replaceable. Ultimately Doflamingo proved to be a thoroughly narcissistic sociopath who's incapable of ever placing anyone else above himself.

Non-Canon (Movies, OVAs and Video Games)

 * In the Episode Of Alabasta anime film, Sir Crocodile demonstrates the cruelty he shows in canon but with none of the mitigating qualities he'd later show. The head of the criminal organization known as Baroque Works, Crocodile formulates a plan to take over the country of Alabasta to discover the location of the ancient weapon, Pluton. Using the illegal Dance Powder, Crocodile creates a drought throughout all of Alabasta except for its capital, Alubarna, deceiving its citizens into believing King Cobra is stealing rain from the rest of the country. He then has Mr. 2 and several other Baroque Works agents disguise themselves as King Cobra and the Royal Guards, ordering them to burn the town of Nanohana to the ground and wound as many innocents as they can to goad the rebel army into going to war. Crocodile later reveals that he hid a bomb within Alubarna that when set, will destroy the town square and kill thousands of rebels and guards alike. When Kohza, leader of the rebel army, finds out about Crocodile's plan, Crocodile mortally wounds Kohza, and stomps on his chest to torture him. He then mocks Vivi for being unable to stop the war or save the kingdom before he drops her off the top of the palace.
 * In Episode Of Chopper, Wapol, as in canon, was the former king of Drum Island. To control the citizens of Drum, Wapol forced 20 doctors into servitude and ordered the exile of all other doctors from the country. In an attempt to have Dr. Hiluluk executed, Wapol lies that all 20 doctors under his service are ill, leaving sick citizens to suffer, all to trick Hiluluk into coming to the castle. When Dalton insults Wapol for laughing at Hiluluk's suicide, Wapol has Dalton beaten to near death before imprisoning him. When Blackbeard attacks Drum Island, Wapol abandons the kingdom to its fate, taking the 20 doctors with him. Returning to Drum Island intending to continue his reign, Wapol decides that the citizens of Drum have became too insubordinate. As a result, he makes a plan to detonate his brother's spore bomb in an attempt to poison all of the citizens of Drum, with only those who beg getting an antidote. When Musshuru begs for Wapol's help after being defeated by Luffy, Wapol simply eats his brother to gain his powers and attempts to detonate the spore bomb, deciding to poison every citizen to death. A cruel and selfish tyrant, this interpretation of Wapol proves to be far more heinous than his canon counterpart.
 * The aforementioned Musshuru, Wapol's older brother, was exiled from Drum Kingdom at the age of 13 for detonating a spore bomb and killing countless innocents to kill his boredom. When Wapol frees him from his exile and brings him back to the country so they can regain control, Musshuru suggests that they cause an avalanche as a way to make their presence known. After arriving at a village destroyed by the avalanche, Musshuru is disappointed that only one village was destroyed. When Wapol suggests the two poison every citizen of the country to death, Musshuru gleefully agrees with the idea, stating that it would be fun to launch the bomb. During his fight with Luffy, he unapologetically poisons Chess and Kuromarimo with his spores when they get in the way of his attack.
 * In Episode of Sky Island, lacking any of the redeeming qualities he has in canon, Eneru is the tyrannical ruler of Skypiea. After destroying his home island, Eneru and his followers invaded Skypiea and overthrew the benevolent ruler, Gan Fall, before taking over. Under Eneru's rule, all outsiders who enter Skypiea are ordered to be killed. Eneru also forces all of Gan Fall's men to work on the flying ship, Ark Maxim, intending to have it take him to the moon. When Ark Maxim reaches completion, Eneru kills them all, along with all of his followers who were at the shrine. During Eneru's survival game, he eliminates enemy and ally alike before powering up Ark Maxim in an attempt to reach the moon. He then destroys a populated city as a show of power, before attempting to destroy all of Skypiea solely for his own amusement.
 * In the movie Baron Omatsuri And The Secret Island, The Lily Carnation is arguably the darkest and most malevolent villain in the franchise. An ancient plant-like horror, Lily made a deal with Baron Omatsuri to resurrect his crew, the Red Arrow Pirates, in exchange for feeding on people. To feed Lily, Omatsuri turns the island into a resort for pirates and makes them compete in the Trials of Hell to wear down their willpower, turning the crews against each other and lured away so that Lily can devour them. However Lily in truth twists the deal that they made with Omatsuri as they revived his crew as nothing but plant-based zombies with no free will of their own and sets out to devour all of the Straw Hat Pirates in order to satisfy its hunger for human flesh. Hailing from the movie viewers considered the closet thing to a One Piece horror film, the Lily Carnation is a mysterious and sadistic fleshing-devouring monster whose very origins are mysterious to even the world itself.
 * One Piece: Pirate Warriors 2: Marshall D. Teach, otherwise known as Blackbeard, lacks any of the care for his crew and redeeming qualities he had in canon and trades them in for being a power-hungry and chaos-loving psychopath. Forming an alliance with Enel and Gecko Moria, Teach uses the Frenzy Dial to conjure a special gas that turns any who inhale it into evil violent versions of themselves and then obtains the Control Dial to allow Teach to control the actions of those affected by the gas. After a major conflict happens between Luffy, Whitebeard and their allies against the Marines, Teach steals the Frenzy Dial and uses it and the Control Dial to brainwash Whitebeard into turning against his own crewmates, crew he considers sons, and then kills him to obtain his Tremor-Tremor Fruit powers when he breaks free of his control. Teach, now possessing his two Devil Fruit powers and both the Frenzy and Control Dials, plans to plunge the world into utter chaos and bloodshed in order to become the Pirate King and slaughter all those who stand in his way, even throwing Enel and Moria under the rug when they are defeated.