#1: DOCTOR HARLAN FONTAINE (La Noire):
Fontaine is one of the most cold and ruthless characters in the game, obsessed with power and manipulation. He constantly utilizes people to further his ends, as seen by his keeping Elsa Lichtmann addicted to drugs in order to investigate the breakdown of an addict and using Lou Buchwalter for the Fund, causing his death. He is also a master at manipulating people, demonstrated by how he convinced Courtney Sheldon to give him the stolen army surplus morphine in blatant abuse of his trust. Furthermore, he manipulated Ira Hogeboom to assist in the Fund's nefarious plans.
And when Sheldon confronted Harlan about the Suburban Redevelopment Fund, Fontaine easily played on Sheldon's trust. Tricking him into thinking he was innocent, and using the opportunity to inject and overdose Sheldon with morphine, killing him (and after all they been though)..


#2: HANNIBAL LECTOR:
Lecter is possibly the most intelligent human alive, possessing an intellect that cannot accurately be gauged by any test known to man. He is an expert in psychology (though he does not believe it to be a science) and is able to frighten, manipulate, and bend others to his will with mere words. He is also able to use his immense presence and commanding but subtle personality to great effect..


#3: NORMAN BATES (spoilers):
Bates suffered from Dissociative Identity Disorder and psychotic behavior, believing himself to be his controlling Mother. At the same time he suffered from visual and auditory hallucinations, in which his mother apparently talked him into committing acts of violence in order to appease her. When the Mother personality took over, Bates would fly into murderous rages targeting women who aroused him, usually whilst dressed in her clothing. He is known to have eventually killed his mother and kept her mummified corpse in the basement of his house for many years..


#4: PAZUZU (Excorist):
Pazuzu is supposedly the evil spirit that possesses the young girl Regan MacNeil. He loves to install to torture his victims as much as possible and to install as much fear as he can..


#5: PINKAMENA: (Cupcakes):
Cupcakes is a very, very dark parody of MLP.
Pinkamena is a evil version of sweet Pinkie Pie.
She is an evil genus, secretly turning people into Cupcakes by using a room that's something out of TEXAS CHAINSAW MASSACRE. In the orginal story she horribly murders Dash, and it's clear she's been doing this for a LONG time.
She's become one of the most famish internet villains of MLP. I myself use her in a lot of things. Including a parody series of GRAND THEFT AUTO. In witch she's Trevor's closest friend, and it's HIM who made her this way, he watches her muder, steal, and eat people.. And only becomes more and more proud of his little "pet"..


#6: THE EMPERIOR (Star Wars):
Emperor Palpatine A.K.A. darth Sidious is the most evil and wicked of all villains in Star Wars. He had the most vicious and evil apprentices, including Lord Maul (ruthless and tactical) and Count Dooku (majestic and corrupt)... He also engineered the execution of the entire Jedi order and anyone who would oppose him in majestic Boss-like fashion in Order 66; he took complete control of the senate and pretty much the entire Galactic Order. He savagely and ruthlessly ruled and conquered the republic and set forth a new Federation led by Grand Moff Tarkin and his forces; He was a master of the Dark Side and the most eloquent and ruthless leader of the Sith order; he even knew of the Sith legends such as Darth Plagueas... And he was responsible for concocting the brilliant takeover of the universe and forced the only remnants of the Light Side Jedi to go into hiding for approximately 20 years; every one of the highest ranking of the Jedi council was literally butchered and slaughtered by his direct orders, including, but not limited to: Mace Windu, Ki-Adi-Mundi, Qui-Gon Jinn, and a slew of others. He managed to defeat Yoda and send him into hiding, which caused him to be defeated in the future... In a majestic twist of fate; his own fate sealed as a result of his ruthless actions and desire to live longer and control the entire galaxy with an iron fist. He was also the reason why Anakin became Vader and pretty much set the entire plot in motion..


#7: PENNYWISE THE CLOWN:
Unlike many horror monsters before him, Pennywise the Dancing Clown was never against killing children. In fact, he actually preferred to kill children as they were an easier target. That was probably why he chose the form of a clown, a figure that both entertained and terrified many young children. It had razor sharp teeth that he could use to kill people..


#8: FRIEZA (Dragon Ball Z):
Frieza is a polite, yet an extremely sadistic individual, taking great delight in slaughtering and destroying others, particularly on a massive scale. This is best shown when he laughed in delight as he watched Planet Vegeta blow up from his Death Ball. Frieza also enjoys making people suffer before killing them, which is why he does not kill his foes outright. A notable fact is that he has tortured every character to fight him..


#9: XERXES (300):
This depiction of Xerxes is portrayed as a power crazed, overconfident, and megalomaniacal psychopath, incredibly determined to conquer the known Persian world. He is extremely arrogant, and overconfident, to believing he is literally a divine being, an overconfidence that has cost him on a number of occasions..


#10: KRUGER (Elysium):
Known for being a ruthless mercenary, Kruger has a knack for killing and enjoys watching his targets brutally die. He's also mentioned to be a rapist, though it's never shown..