Marvelous Marvin Hagler (born Marvin Nathaniel Hagler) was an American professional boxer and film actor who competed in boxing from 1973 to 1987. He reigned as undisputed champion of the middleweight division from 1980 to 1987, defeating 11 opponents, all but one by knockout, and making twelve successful defenses of that title. Hagler also holds the highest knockout percentage of all undisputed middleweight champions at 78 percent. His undisputed middleweight championship reign of six years and seven months is the second-longest of the last century, behind only Tony Zale, whose reign included several years of inactivity during his service in World War II. Nicknamed "Marvelous" and annoyed that network announcers often did not refer to him as such, Hagler legally changed his name to "Marvelous Marvin Hagler" in 1982.

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Hagler is an inductee of the International Boxing Hall of Fame and the World Boxing Hall of Fame. He was twice named Fighter of the Year by The Ring magazine and the Boxing Writers Association of America, as well as Fighter of the Decade (1980s) by Boxing Illustrated magazine. In 2001 and 2004, The Ring named him the fourth greatest middleweight of all time and in 2002 named him the 17th greatest fighter of the past 69 years. The International Boxing Research Organization rates Hagler as the sixth greatest middleweight of all time, while BoxRec rates him the 29th greatest boxer of all time, pound for pound. Many analysts and boxing writers consider Hagler to have one of the most durable chins in boxing history, having been knocked down only once during his entire professional career. The lone knockdown, scored by Juan Roldán of Argentina, is still being disputed.

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On March 13, 2021, Hagler's wife, Kay, announced that Hagler had died at his home in New Hampshire. His son James "said his father was taken to a New Hampshire hospital after experiencing chest pains and difficulty breathing." Thomas Hearns deleted an Instagram post alleging that the covid vaccine Hagler had received was the cause. Hagler's widow denied that the vaccine had anything to do with her husband's death. He was 66.   Source.