Despite his young age, King Joffrey Baratheon stood out as one of the vilest characters in the series. While always shown to have a darker side, Joffrey finally crossed the line when he had Ned Stark executed, ensuring that the war with the Northerners would never reach a peaceful conclusion. Joffrey not only did this in front of Ned's daughter, Sansa, Joffrey's own fiancée, he then forced her to look at the decapitated heads of her father and household afterwards. This was then followed by a long period of Domestic Abuse during which Joffrey had her regularly beaten by his Kingsguard and threatened to rape her even after she married his uncle, Tyrion. As king, Joffrey reveled in his power over life and death, and his reign was filled with all manner of pointless cruelties. Joffrey's crimes included having a minstrel whose song offended him choose between losing his hands or his tongue, attempting to have a drunken knight drowned in a cask of wine, firing on starving peasants with his crossbow, ordering his bodyguard to cut through a crowd of peasants to get at one of them who threw manure at him, nailing antlers to the heads of Stannis sympathizers and firing them from trebuchets as entertainment during the Battle of the Blackwater, and attempting to convince his grandfather to execute everyone who fought against him, regardless of whether or not they surrendered. A budding psychopath who believed being the king gave him the right to do whatever he liked, Joffrey's sadism was so great that he was well on his way to surpassing his predecessor as the next Mad King of Westeros.
Ser Gregor Clegane is an eight foot giant kept in a constant state of rage due to migraine headaches. Alias The Mountain That Rides, Gregor is one of the most feared characters in the setting, and with good reason. He is rumored to have killed his sister when they were children, to have arranged for his father's Hunting Accident, and to have murdered both of his wives. The things that we know he did are even worse. As a twelve year old boy, he burned off half of his younger brother Sandor's face when the latter dared to play with one of Gregor's toys—a toy that Gregor himself, it should be noted, did not want anymore. At seventeen, he dashed the baby Prince Aegon's head against a wall, and then raped and murdered his mother, Princess Elia, with her son's brains still on his hands. At a tournament at the start of A Game of Thrones he kills one of his opponents, and tries to kill another, and that's before he's turned loose on the countryside. He and his men proceed to rape and murder anyone who falls into their hands, often torturing people to see where they have hidden their gold. At one point in A Clash of Kings each day, for ten days, Gregor picks one person from a group of villagers and has his Torture Technician, "the Tickler", question that person over and over, until they die from the torture. One of the villagers, a mother, volunteers to be taken if they will spare her daughter. The next day, he has the daughter questioned too, to make sure the mother didn't leave anything out. Another time he smashes a girl's face in for speaking when he wanted silence, than turns her over to his men to be gangraped for days. When confronted by the brother of Princess Elia, who repeatedly asserts that "Her name was Elia of Dorne. You raped her, you murdered her, you killed her children," Gregor's only concern (besides killing him) is that the man has gotten the order of events wrong.
"Her name was Elia of Dorne. First, I killed her screaming whelp. Then I raped her. Then I smashed her fucking head in. Like this."
Ramsay Snow, the Bastard of Bolton, stands out as one of the most savage and depraved men in Westeros. Suspected of murdering his good-hearted and trueborn brother, Domeric, Ramsay first comes to prominence after he forces the elderly widow, Lady Hornwood, to marry him to gain her lands. Having already killed his new bride by starving her to death, Ramsay only avoids death at the hands of Winterfell soldiers by impersonating his servant, Reek, and sending his "friend" to die in his place. When Theon Greyjoy takes over Winterfell, the imprisoned Ramsay allies himself with Greyjoy and acts as a corruptive influence, ultimately being the one to convince Theon to cross the Moral Event Horizon by murdering two little boys to pass them off as Bran and Rickon Stark. When Ser Rodrik leads Winterfell forces to retake the castle, Ramsay pretends to be an ally only to murder Rodrik personally and has his own forces massacre the confused Northerners. Ramsay then betrays and captures Theon before ordering his men to raze Winterfell and slaughter everyone inside, Ironborn and Northmen alike. One of Ramsay's preferred hobbies is hunting naked, exhausted girls through his father's lands. If the girls give him good sport, he'll rape them then kill them quickly and take their skins as trophies. If they don't give him a good chase he flays them alive after raping them. In fact, flaying people alive is Ramsay's favorite pastime and he engages in it every chance he gets, such as he does to the Ironborn forces occupying Moat Cailin that had surrendered after Ramsay promised them mercy. If he has the time, Ramsay usually flays the flesh off his victims' fingers so that the pain will be so intense that his victims beg him to cut the fingers off completely. Ramsay's psychical and psychological torture of Theon Grejoy is so extensive and brutal that it turns Theon from a cruel Smug Snake into a pathetic, insane wretch that has been conditioned into believing he's the new Reek. No one is safe from Ramsay's cruelties, not even his second wife, Jeyne Poole, the girl who's pretending to be Arya Stark and whom Ramsay abuses despite her being vital for Bolton control of the North. Even her wedding night was filled with torment as Ramsay forced Theon to participate in the bedding. A half-feral beast of a man, Ramsay lives to satisfy his sadistic urges and is so pointlessly and moronically cruel that even his own father, Roose Bolton, only refrains from killing him due to the taboo against slaying kin.
Craster is a particularly vicious Wildling and ally of the Night's Watch (each of whom identifies him as belonging to the opposing organisation) who, in his own words, kneels to no man, including Mance Rayder, King-Beyond-The-Wall. Living alone in a huge, ramshackle compound, Craster keeps a harem of women in line with brainwashing and violence, breaking their spirits until they cannot rise up against him, despite the fact that they vastly outnumber him. All of these women are his "wives"; many of them are also his daughters and granddaughters. When one of them becomes pregnant, Craster waits to see if it is a boy or a girl. If the child is female, he waits until she is old enough (read eleven or twelve) and does his best to impregnate her. If the child is a boy, Craster leaves him in the woods to be killed by the cold or devoured by the Others; this way they cannot challenge his control over the women. Obsessed with his own hedonism, and raising the next generation of wives, Craster uses his alleigance with the Night's Watch to make sure that nobody, not even the Watch, interferes with his business.
The self-styled "Lord" Vargo Hoat is the leader of a psychotic mercenary band, known as The Brave Companions or, more commonly, "The Bloody Mummers." A vicious barbarian with no regard for morals or innocent life, Hoat allows his band to Rape, Pillage, and Burn, at their discretion. Each man in the group is a monster with sickening crimes to his name, but Hoat allows all of them to indulge their darkest desires as long as Hoat profits. Hoat himself has a penchant for maiming victims, having earned the name "Footman" for lopping off the feet of his victims. Hoat initially works for the Lannisters, until he betrays Harrenhal to the Boltons. Once this is done, he has the Lannister commander Ser Amory Lorch fed to a bear. While Lorch was a child murdering pig of a man, all Hoat cared about was the entertainment. When his men capture Jaime Lanninster and Brienne of Tarth, Vargo has Jaime's sword hand chopped off for no rational reason and later tries to rape Brienne himself. When she resists and bites his ear off, he throws her to the bear as well with a useless practice sword. Hoat is feared by all who know him as a vicious lunatic who leads the worst group of beasts posing as men in Westeros, and will kill someone for noticing his speech impediment, for not referring to him as a proper lord, or simply because he thinks it's funny.
Hoat's company, the Brave Companions, are a bad lot, but noselesspaedophiliacserial rapist and serial killer Rorge is acknowledged in-universe and out as the worst of them. Freed from the Black Cells under King's Landing, along with his companion, Biter, Rorge signs on with the Brave Companions after Arya Stark saves him from certain death. He offers to repay her by anally raping her with her own wooden sword, only stopping when she threatens him with Jaqen H'ghar. He later goes against Hoat's own orders when he tries to rape Brienne of Tarth, and tortures the recently crippled Jaime Lannister by kicking him in his stump, when Jaime reminds him that Brienne is supposed to remain unharmed. It's after Hoat's death, though, that Rorge really comes into his own. Taking control of a gang of brigands, he burns down the town of Saltpans, in an act so savage that it shocks the sensibilities of a Westeros long inured to the atrocities of Gregor Clegane and Vargo Hoat. Killing twenty men himself, Rorge rapes every woman and child in town, most notably raping a six year old girl while wearing chainmail; he also rapes nuns before feeding them to Biter. Upon encountering Brienne again, he expresses a desire to "cut off her legs and set her on her stumps so she can watch me fuck the crossbow girl." The girl in question is under ten years old. Sidematerials would indicate that he is also the reason why Biter is the way he is—finding an orphan boy, Rorge removed his tongue, filed his teeth, and made him fight dogs with only his new fangs. A consummate Woman & Child Hater, and a serial predator in a world full of warriors, Rorge earns the enmity and disgust of everyone he meets.
Game of Thrones
Joffrey Baratheon is a dyed-in-the-wool sadist who seems to take pleasure only in fear and suffering. A brief list of his crimes include executing Eddard Stark out of spite, tormenting Sansa mercilessly, slaughtering Robert's bastard children which included infants, threatening to execute his own mother for slapping him, forcing one prostitute to beat another (one possibly to death), and killing Ros personally for crossbow practice. At his uncle's wedding he's threatening to rape Sansa as his men hold her down and seems positively aroused by the prospect of her trying to resist him.
Ramsay Snow, Roose Bolton's bastard son, burned Winterfell to the ground, butchered everyone within and flayed the surrendering Ironborn alive. And that's just what he did off screen. He spends most of season three sadistically torturing Theon Greyjoy both physically and mentally for no reason other than his personal amusement (and perhaps for some manner of sexual depravity), until the man is left nothing but a broken shell stripped of almost everything, including his name. Said torture involves him killing his own men to gain Theon's trust, finger removal and eventual castration of his helpless victim. At some point, he also states that he is going to enjoy hunting down Bran and Rickon, who are on the run.
Walder Frey, while somewhat repugnant in his first appearance, seems to be a fairly competent ruler and willing to help the heroes, for a price. His next appearance even has him come across as a Cool Old Guy, forgiving Robb's slight against him. Then comes The RedWedding, which opens with Robb's pregnant wife being stabbed repeatedly in the stomach, Robb, Catelyn, and the Stark Bannermen being murdered in a massive violation of guest right, laughing and eating the whole time. To top it off, when his wife is held hostage, he simply tells the hostage taker to kill her, she's expendable. To drive the point home, he begins the next episode by recounting the Red Wedding with glee, showing no remorse and celebrating the power his betrayal has brought him.