Tien is a human introduced at the end of the Foutrune Teller Baba Saga in the anime and manga. Because he was brought up harsh, he is cold and heartless when first met,

Tien's Tri-beam

thinking nothing of harming innocents and inflicting pain. Master Roshi  and Goku eventually help him to see the wrong in his teachings, and he then becomes a trusted ally. He fights as a Z fighter, but retires from fighting after Goku and Vegeta become Super Saiyans.