In the novel "In the Time of the Butterflies," Rafael Trujillo is called "El Jefe." Why? In what ways did he act like an "El Jefe"?

"El Jefe" means "The Chief", and it is a fitting nickname for Rafael Trujillo, who ruled the Dominican Republic from 1930 to 1961.  Trujillo sought total control over all elements of government and the lives of his people, and was ruthless in erradicating dissent and eliminating obstacles that stood in the way of his goals. 

Trujillo rose through power by way of the military, and as Sinita explains, "all the people who were above him kept disappearing until he was the one right below the head of the whole armed forces".  Through ruthlessness and trickery, he quickly became the actual head of the armed forces, and then soon announced himself president of the country (Chapter 2).  An incorrigible womanizer, he kept mistresses in opulent palaces around the island, and his government was characterized by corruption and greed.  When faced with opposition, such as that represented by the movement in which the Mirabal sisters were involved, he responded forcefully and unscrupulously, putting those who dared to rebel under surveillance, imprisoning them, and, as in the case of Minerva, Patria, and Maria Teresa Mirabal, ordering their executions.