Master Shen

Shen trained alongside Roshi under the legendary Master Mutaito in their youth. While Roshi took away lessons about discipline, humility, and the responsible use of martial arts, Shen gravitated toward the darker applications of their training. The two parted ways and founded rival schools, with Shen's Crane School teaching its students that martial arts existed as a tool for domination, personal gain, and killing.

Shen's grudge against Roshi intensified after the death of his brother, Tao Pai Pai (Mercenary Tao), whom Goku seemingly killed during the Red Ribbon Army saga. At the 22nd World Martial Arts Tournament, Shen brought his two star pupils, Tien and Chiaotzu, with the specific intention of having them destroy Roshi's students. He ordered Chiaotzu to use his psychic powers to interfere in Goku's matches and instructed Tien to kill his opponents rather than merely defeat them.

Shen's plan unraveled when Tien rejected his philosophy during the tournament. Moved by Roshi's words about the true purpose of martial arts and shaken by the cruelty his master demanded, Tien chose to fight honorably. When Tien refused to kill Goku after their final match, Shen was furious and attempted to intervene, only to be expelled from the arena by Roshi.

After losing his best students, Shen appeared briefly during the King Piccolo saga, allying with his returned brother Tao (who had survived Goku's attack and been rebuilt as a cyborg). Both were easily defeated, and Shen faded into irrelevance as the series' power scale left him far behind. His lasting impact on the story is through the students he shaped: Tien and Chiaotzu became heroes not because of his teachings, but in spite of them, and their rejection of the Crane School's philosophy is one of the earliest redemption arcs in Dragon Ball.