General Tao was a deadly assasin who fought Goku. He was defeated however and needed to be transformed into a cyborg to survive.
Never killed.
Defeated by Goku.
After Tao became a cyborg, he disconnects his left hand to reveal a retractable knife. When Tien was slashed by this sneak attack, he claimed that Tao has lost his honor and pride of a warrior. Due to his use of this technique during the 23rd World Martial Arts Tournament, Tao lost his tournament match with Tien by disqualification for violating tournament rules banning the use of weapons.