When Mr. Bignone was handed the reins on July 1, 1982, the military junta that had engulfed Argentina in repression and economic chaos was on its last legs.
Mr. Bignone, who had retired from the military in 1981, was asked by the military leadership to succeed Gen. Leopoldo Galtieri, who in 1982 led Argentina to embarrassing defeat when British forces repulsed an invasion of the British-held Falkland Islands.
Mr. Bignone took over with the stated goal of transitioning to a democratically elected civilian government. On Dec. 10, 1983, he handed power to Raúl Ricardo Alfonsín, who had been elected in late October.
Before the transition, however, Mr. Bignone led a methodical process not only to destroy evidence about the dictatorship’s crimes but also to justify its repression. He approved an amnesty that was effectively an effort to shield military officers from prosecution.
Mr. Bignone’s convictions in 10 war-crimes trials led to three life sentences and seven sentences of 15 to 25 years. He was also acquitted in one case and indicted in nine others that never went to trial, according to data from the Argentine attorney general’s office.
“Death was left without its last boss: The genocide perpetrator Bignone died,” Hijos, a human rights group that advocates for descendants of the disappeared, wrote on Twitter. “His family knows the time, the reasons and the location. It can also decide where to bid him farewell. The thousands of families who are Bignone’s victims can’t.”
Mr. Bignone’s convictions and sentences marked a stark shift in how Argentine society regarded him. He had once been seen as the most benevolent member of the military junta because he had led the transition to democracy, but he came to be reviled when his key role in the darkest chapters of the dictatorship became clear.
Mr. Bignone was sentenced to prison for the first time in April 2010 after being found guilty of torture and killings as the head of the Campo de Mayo military base, where illegal detention centers had held thousands.
He had also led the military takeover of the Posadas Hospital in Buenos Aires Province, where another illegal detention center was set up.
In 2016, Mr. Bignone was sentenced for his role in Operation Condor, a joint effort by right-wing dictatorships in the region to track down dissidents.
He never expressed regret for his crimes. In a memoir, “The Last De Facto” (1992), he sought to justify the actions of the juntas.
He did so again before being sentenced in 2010, saying that there had been an “irregular war” underway in Argentina at the time and that the armed forces “had to get involved in the fight to defeat terrorism.”
Reynaldo Benito Bignone was born on Jan. 21, 1928, in Morón, Buenos Aires Province, and entered the Military Academy at 19. He went on to become general secretary of the Army and was named head of the Military College months before the 1976 coup that ousted President María Estela Martínez de Perón.
Argentina’s Defense Ministry stripped Mr. Bignone of his military rank in October 2014.
He is survived by two of the three children he had with his wife, Nilda Raquel Belén Etcheverry, who died in 2013.