Tao Pai Pai is a legendary assassin-for-hire and the younger brother of Tsuru-Sen'nin. The Red Ribbon Army brought him in to steal Goku's Dragon Balls and kill the kid, which he almost managed—he beat Goku down and grabbed nearly all the balls, but one slipped away and ended up saving Goku's life when Tao went for the finishing blow.
Three days later, Tao came back for that final Dragon Ball. Problem was, Goku had spent those three days training under Karin and came back way stronger. The fight didn't go Tao's way, and when he tried to finish things with a grenade, Goku just bounced it right back at him. The explosion left Tao badly hurt.
That's where his older brother stepped in—Tsuru-Sen'nin rebuilt him as a cyborg. Tao competed in the 23rd Tenkaichi Budokai and came in swinging hard, brutally taking out Chaozu. But his next opponent, Tenshinhan, proved to be his match. Tao even managed to cut Tenshinhan's chest with a knife, giving him a scar that stuck around, but Tenshinhan disarmed him and won the fight.
Tao shows up again later during the Cell Games Saga in the anime. His design ended up being pretty influential too—he's basically the inspiration for Lau Chan from Virtua Fighter.
Content compiled by AnimeList.moe from publicly available sources.