Leo was the brother of Carlos Cruz, a man whom many recognize as one of the greatest fighters to come out of the Dominican Republic. His brother Carlos had conquered the world Lightweight title by beating Carlos Ortiz in 1969, and was on his way to a rematch with Ortiz at San Juan, when his Dominicana De Aviacion DC-9 jet crashed shortly after take-off, killing everyone on board. With that, Leo had to learn how to deal with life's hardships at a very young age (see: Dominicana DC-9 air disaster).
Leo moved to Puerto Rico early in the 1970s, and began identifying himself as half Puerto Rican almost immediately. He began his successful professional boxing career there, with a string of wins. Despite having beaten future two time world champion Lupe Pintor, however, Cruz was still a virtual unknown when given a chance to win the WBC world Jr. Featherweight championship. Despite losing by a knockout in the 13th round against world champion Wilfredo Gomez, his stock around the boxing world rose after that fight. Cruz kept on fighting, and winning, until he was given a second world title try, this time by the WBA world champion Sergio Palma, in Buenos Aires. Cruz was beaten by a decision in 15 by the Argentine world champion, but in a rematch on February of 1982 at Miami, Cruz became world champion by defeating Palma by a decision, also in 15 rounds.
Cruz in his first defense knocked out Benito Badillo of Chile in eight rounds, at Roberto Clemente Coliseum in San Juan. When Gomez left his WBC title vacant soon after, Cruz became recognized by most fans as the universal world champion. Then, he defeated South Korean challenger Seoung Hoon Lee, by decision in 15; after dropping him in round eight; also in San Juan. In his first defense at his home country, Cruz put his title on the line on August of 1983 against Nicaraguan challenger Cleo Garcia at Santo Domingo. Cruz retained the title by a decision.
With a lucrative defense against Puerto Rican Victor Luvi Callejas looming ahead, Cruz went to Rome in February of 1984, and, while defending his crown against Italian Loris Stecca, he inexplicably quit in round 12, therefore losing the world Featherweight title.
Cruz attempted a comeback in 1985, winning one fight, but retiring for good after that.
Also see: Eleoncio Mercedes.