1. The Joker :
the Joker is portrayed as a master criminal whose characterization has varied. The original and currently dominant image is of a highly intelligent psychopath with a warped, sadistic sense of humor, while other writers have portrayed him as an eccentric prankster. The Joker has been referred to as the Clown Prince of Crime (or Chaos)The Joker's victims have included men, women, children, and even his own henchmen and other villains , he is reported to have killed well over 2,000 people.
The Joker commits crimes with comedic weapons such as a deck of bladed playing cards, an acid-squirting flower, cyanide-stuffed pies, exploding cigars filled with nitroglycerin, harpoon guns that utilize razor-sharp BANG!-flags, and a lethally electric joy buzzer. His most prominent weapon is his Joker venom, a deadly poison that infects his victims with a ghoulish rictus grin as they die while laughing uncontrollably.
2. The Dahaka ( Prince of persia ) :
In Prince of Persia: Warrior Within, the Dahaka serves as the physical manifestation of the inevitability of fate and is also a primary antagonist in the second ending. The Dahaka appears to be a massive, black humanoid creature with horns. The Dahaka has a weakness to water, and can only be killed by the legendary Water Sword, found by the Prince if the player obtains all life upgrades, unlocking the second ending. The beast is the guardian of the timeline, and seems to appear only when the timeline is disrupted.
3. Diablo ( Diablo ):
He known as the Lord of Terror ,Diablo is a large humanoid demon, he is an alchemist, he wanted these secrets to research mutation and unleash mutants in Vizima. His abilities include disguise as other humans, open portals and using fire magic.
4. Kain (legacy of kain ) :
Kain is a fictional character and the titular character that appears in the Legacy of Kain series of video games. Depending on the game and its viewpoint, Kain has been either the central protagonist, or an antagonist, but in all his depictions he is an anti-villain, interested only in his own goals.
A noble murdered and revived as a vampire, Kain embarked on a crusade to kill his assassins and then be restored to human form. When he came to realize how much horror and hypocrisy lies in humans hearts, Kain turned his back on his prophesied duty and became a vampire lord ruling over the land.
His powers : All vampires in Nosgoth have their own unique Dark Gift; a supernatural power. Kain's Dark Gift was the ability to use surrounding mist to assume a mist form, which allowed him to be virtually invisible and intangible. He also had a fury ability where he could use a single charged attack against an enemy.
5. Sweet Tooth( Twisted Metal ) :
Sweet Tooth, real name Marcus 'Needles' Kane, is designed around the premise of a killer clown that drives an ice cream truck,
The ice cream truck was actually designed well before the driver himself, and Black's incarnation took six months and many concept sketches to finalize. Labeled early on "DEMONIC ICE CREAM TRUCK", attention to details such as the head adorning the vehicle and the contents of the back of the truck were focused on during development.
6. Sephiroth ( Final Fantasy) :
In Final Fantasy, Sephiroth is the result of an experiment by the mega-corporation Shinra, in which they used cells from the extraterrestrial lifeform Jenova. Because he gets upset about being an experiment, Sephiroth decides to become a god to take control of the planet; Cloud and the game's other protagonists choose to stop him.
he uses Masamune an a weapon and he is a 1st rate soldier .
7. GLaDOS ( Portal) :
For much of Portal, GLaDOS is a voice that acts as a narrator and guide for players. Her voice is robotic, but distinctly female. Over time, players learn that she is in fact leading the player-character Chell to her death. Her personality has been described as passive-aggressive, witty, narcissistic, and sinister. She has a number of system personality cores installed into her, partly in order to prevent her from killing anyone (other than the ones she already did before the failsafes were installed). Eventually, once the player encounters her, she is revealed to be a complex computer, with robotic parts hanging from a larger device.
8. Andrew Ryan (BioShock) :
Andrew Ryan has strong ideals, so much so that they are the most important thing to him, trumping his own life. He has an irrational hatred of what he refers to as "parasites," consisting mainly of people who support left-wing politics; namely socialism and communism. Ryan also has a vast hatred for the religious, but more notably the altruistic, as he believes altruism to be the root of all evil.
Ryan is a strong supporter of Liberty, as he believes all individuals have the right to act according to how they see fit, with "parasites" being the only ones who would attempt to deny mankind that of free will. Ryan accentuates this belief to the extreme, denouncing all laws.One of Ryan's main ethics is that of free market, asserting that all industry should be kept completely unfettered by government intervention. Ryan is also a vociferous capitalist, believing capitalism to be the only way an economy can flourish successfully.
9. Albert Wesker ( Resident Evil ) :
Power-hungry, knowledgeable and infinitely cunning, Albert Wesker was a man who sought power and domination over the entire human race, all for his own gain. To this end, he was affiliated with the Umbrella Corporation, as one of its most promising researchers, and at the same time participated in illicit activities by going undercover as an officer in the RPD and the leader of S.T.A.R.S. in Raccoon City. Through the course of much betrayal of his allies to further his own plans, Wesker faked his death, gained superhuman powers from an experimental virus, and worked alongside both the mysterious "Organization" and Tricell, Inc. He would eventually enact a plot, originally created by Ozwell E. Spencer, to transform the human race into powerful superhumans like himself. Wesker is the main antagonist, surpassing even Ozwell E. Spencer.
10. Saren Arterius( Mass Effect ) :
Saren Arterius is the longest serving turian member of the Spectres - the elite military operatives answering directly to the Citadel Council. For 24 years he has been an agent of the Council's will, a zealous defender of galactic stability in the unsettled border region of the Skyllian Verge.
Official records of Spectres are sealed, but it is known that Saren followed turian tradition and entered the military at the age of 15. In 2155 he was promoted to active service after only a year of training, though it is unclear whether his unit was involved in any of the battles against human forces during the First Contact War of 2157.
In 2159 he became the youngest turian ever accepted into the Spectres. Intelligent, cunning and capable, Saren quickly developed a reputation for ruthless efficiency. Although there were a number of unsettling rumors about the brutality of his methods, there was no denying his results.
In recent years Saren has become an outspoken opponent of human expansion. Like many other non-humans, he believes the Alliance has become overly aggressive in its efforts to establish the people of Earth as a dominant species in Citadel space. As a Spectre it is generally believed he will continue to follow the will of the Council in this matter, but there are some - particularly among the Alliance - who fear Saren may soon decide to take matters into his own hands.
Powers and Weapons:
Saren is a Spectre, a title for the Special Tactics and Reconnaissance unit of the Citadel Council. The status of Spectre means that he answers directly to the Council which is the highest authority in the galaxy or he did before he went rogue. Through this, Saren has had extremely specialized training and has contacts all over the galaxy, giving him access to a wide array of weapons and resources. He served as a Spectre for twenty-four years.
Before his life as a Spectre, Saren Arterius was in the Turian military. When he encountered Sovereign and decided the only way to save the organics in the galaxy was to side with the Reaper. He allowed the vessel to install 'upgrades' in him, giving him access to powerful biotic powers(telekinesis, barriers, ect).