As dictators go, Augusto Pinochet was the least worst option for Chile in 1973. With Salvador Allende Gossens consolidating his power despite the Chilean Parliament contesting his increasing authority, and with Allende ignoring more than 7,000 court orders and legislative enactments, the Chilean military of which Pinochet was the commander in chief, struck in September 1973 to depose the emerging Communist dictator at the behest of the Parliament that Allende had flagrantly ignored. In so doing, Pinochet saved the nation from a Castro protege who had begun to run a fairly prosperous nation into the ground as Chavez is now doing in Venezuela and as Castro had done in Cuba.
Unquestionably, the blood on Pinochet's hands is somewhat thick: 3200 dead, 27,000+ tortured. That's the downside of the non-bloodless coup. Nonetheless, about 2700 of those deaths occurred during the brief civil war that broke out in 1973, only 500 in the next 17 years of Pinochet's rule.
Pinochet exemplified the doctrine that "he may be a sonofabitch but he's OUR sonofabitch" that underlay US indulgence of certain despots during the Cold War. But Pinochet's reign led to substantial benefits to Chile: a stable market economy that became the best by far in Latin America, prosperity that far outstripped the rest of the continent, and a stable democracy. None of those outcomes would have occurred under the Castroite Allende.
Reviled by the Left, Pinochet's bad acts are ugly. Then again, for those who want to play numbers games: the Argentine junta of the same era killed no fewer than 9,000; Castro's bloody hands account for upwards of 60,000 dead; Idi Amin (lauded as a "splendid type" and good footballer by the British Foreign Office upon obtaining power) killed 300,000; Mao's Cultural Revolution of 1966-68 caused no fewer than 500,000 deaths (and more likely many times that number); and the Khmer Rouge that Noam Chomsky continually lauds massacred 2,000,000 of Cambodia's 5,000,000 people.
Unlike Castro, Chavez, Ortega and the other Latino dictators-for-life (or wannabes in Ortega's case), Pinochet voluntarily left office in 1990 after losing a democratic referendum (that he did not rig -- see Chavez, 2001) and bequeathed a democracy to Chile. The referendum was essentially popularly forced upon Pinochet by the middle class in Chile that had flourished since economic reforms in the early 1980s.
He was corrupt (as Swiss bank accounts later showed), occasionally ruthless, and a dictator. And he left power voluntarily.
Chile is the model economy of Latin America, and now even the model democracy. Neither of those facts would have come to be without Pinochet.