Santiago Carrillo, who evolved from a bomb-throwing opponent of Gen. Francisco Franco and his fascist forces into a Spanish Communist leader who promoted a more moderate, democratic European Communist Party independent of the Soviet Union, died on Tuesday at his home in Madrid. He was 97.

The cause was heart failure, his son Santiago said.

Born into a socialist family in dynastic Spain, Mr. Carrillo converted to Communism and fought Franco’s fascist forces during the Spanish Civil War, leaving him haunted by a massacre on his watch. When Franco came to power, Mr. Carrillo was forced to retreat to Paris, but he continued to manage the Spanish Communist Party from there, becoming its secretary general in 1960....