Nina Williams is an anti-heroine of the Tekken series and a supporting antagonist in both Tekken 6 and Tekken 7. She is also the rival of Anna Williams and the mother of Steve Fox. She is one of four characters along with Heihachi Mishima, Paul Phoenix and Yoshimitsu who appeared in all Tekken games.
Nina is a silent assassin. She learned assassination techniques from her father and Aikido from her mother. She was sent to assassinate Heihachi Mishima, the sponsor of the King of Iron Fist Tournement.
Nina ran away from her home in Ireland, because she hated her sister Anna. The unknown organization paid her well to kill Kazuya Mishima. She agreed when she learned that Anna worked with Kazuya as his bodyguard. Her father Richard, before his death, asked her to stop fighting with her sister but she refused. Nina entered to the King of Iron Fist Tournament 2 to kill Kazuya and defeat Anna.
In the last tournament Nina had to assassinate Kazuya, but her quarrel with Anna prevented her success. Then she was captured by Kazuya's corps and was used as a guinea pig in Boskonovitch's Cold Sleep #2 experiment. She was awakened by Tekken Forces and she sensed Ogre's presence. Nina was controlled by Ogre and she entered to the King of Iron Fist Tournament 3 to assassinate Jin Kazama.
After the King of Iron Fist Tournament 2 Mishima Zaibatsu used Nina in the Cold Sleep experiment. After she awakened she suffered from cryosleep-induced amnesia. After the King of Iron Fist Tournament 3 she escaped from the Mishima Zaibatsu and again became a contract assassin. She couldn't regain memories of Anna and her previous life. The only thing she could do was execute her contracts for money. One day Nina accepted a contract from the Mafia. Her target was Steve Fox, a world boxing champion. When she learned that he will be in the King of Iron Fist Tournament 4, she entered the tournament.
In previous tournament Nina learned that Steve Fox was her biological son, but she felt nothing. Shortly after the Sindricate fell and left her with no purpose. Nina decided to meet Anna to try to recover her past. But when she saw her they started fighting. In the end they agreed to settle their rivalry in the King of Iron Fist Tournament 5.
Nina finally defeated Anna in the previous tournament. When Jin Kazama became leader of the Mishima Zaibatsu, he recruited her as a member of his special forces, and she helped him in taking over the world. Nina entered to King of Iron Fist Tournament 6 to eliminate anyone who poses a threat to Jin.
Nina first appears as the de facto leader of Mishima Zaibatsu during the prologue, with Jin absent, Nina attempts to organize the troops against G Corporation, questioning whether Jin's decision to wage war truly saved the world, as it continued to drag on after Azazel's defeat. Eventually, the Zaibatsu would find itself under attack by Heihachi Mishima. Defeated by Heihachi, she relents to his statement that only he can save the Zaibatsu in the war against Kazuya and is hired by Heihachi to serve the Zaibatsu. Helping him broadcast his public return and that of the King of Iron Fist Tournament, she joins him in attacking the Sirius Marksmen after their leader made constant rejections to their invitations.
After the Sirius Marksmen aid the Zaibatsu, Nina finds footage that confirms that Jin is in the custody of Lars. As Lee is aiding Lars's resistance, the Zaibatsu makes an initial attack on Violet Systems, however, it fails. Nina is then sent to lead the second assault. She faces Alisa numerous times in her attempt to retrieve Jin, however, after multiple rounds, Lee and Lars tell Nina that she has failed once again, and that Jin had now been successfully extracted. Knowing that Heihachi would not tolerate the failure, Nina opted not to return back to the Zaibatsu, wondering with interest at how the events will eventually play out.
Nina's persona seems to be cold and indifferent. In fact, she had been drugged by an underground force when she was young in order to create the perfect assassin, killer, and murderer, regarding the chronology of Death by Degrees. Her bitterness towards men could be a result of her deflation after Tekken 2. The only man she had ever trusted was her father, who died shortly before Tekken 2. Ironically, after her father's death, Nina was brainwashed, controlled, and possessed by Ogre. Thus, she was unable to feel any emotion at all. Nina's personality remains monotonous yet sadistic when it comes to teasing her younger sister Anna.
Nina's win poses range from tomboyish and masculine to flirtatious, usually by placing a foot on top of the opponents body or showing off her body figure. Although she is an assassin, most of her missions are inclined for the good of the world, though she was hired to kill and assassinate her only son named Steve Fox, (the grandson of Richard Williams and Mrs. Williams) by the syndicate during Tekken 4 and also assisted Kazuya's son Jin Kazama when he started a world war during Tekken 6.
- In The Tekken Chronicle Book, Nina's hair color is brown instead of blonde and her occupation is listed as a boxer instead of an assassin.