Android 17

Android 17 (人造人間１７号, Jinzōningen Jū Nana-go) is Dr. Gero's seventeenth creation (although he is a cyborg), Android 17 was designed to serve Gero's vendetta against Goku, who overthrew the Red Ribbon Army as a child. Despite his interests not deviating from this expectation, Android 17 takes it upon himself to kill Dr. Gero who is uncooperative with Android 18's curiosity in activating Android 16.

Android 17 makes his debut in "The Androids Awake!", the 349th chapter of the Dragon Ball manga, issued on March 10, 1992. He makes his first animated appearance in "Nightmare Comes True", the 133rd episode of Dragon Ball Z, which premiered on April 8, 1992.

Android 17 has shoulder-length black hair and blue eyes. Underneath his hair, he has two gold hoop earrings. Around his neck, he wears an orange bandanna. He wears a short sleeve black shirt with the Red Ribbon Army's logo, and underneath, he wears a long sleeve white shirt. He wears a belt to hold up his blue jeans which have a tear just above the knee of the left leg. Just below the first belt he wears another belt with a gun holster and another pouch. 17 wears green socks and blue and white shoes. During his cameo in the Buu Saga, he wears a blue jacket and, during the Super 17 Saga, he wears a tan, knee-length jacket.

Initially a reckless anarchist, 17 later reveals himself to be little more than a rebel without a cause. When he is revived by Shenron because of a wish that restored both the lives of all of Cell's victims and all the damage caused during the Cell Games, Android 17 goes on to live a life of peace in obscurity. At the end of Dragon Ball Z, 17 provided energy for Goku's Super Spirit Bomb to destroy Kid Buu. He reappears in Dragon Ball GT when scientists Gero and Myuu brainwash him telepathically and he is eventually merged with Hell Fighter 17, a Machine Mutant version of himself created by the scientists in Hell. Yet even without the ability to maintain his mind, 17 still exhibits some of his sensitivity. This is in stark contrast to his alternate self from Future Trunks's timeline, where he is a murderous sociopath who cares for no one but himself and 18. Android 17 is considered a Z Fighter, mainly because he has killed sinister characters such as Dr. Gero (twice) and Dr. Myuu; and he has helped to defeat other major villains such as Cell and Buu. While under Dr. Myuu's control, he forced his transformed-self to reveal his own weak point, thus allowing Goku to kill him.

Information from:
http://dragonball.wikia.com/