The stately, smooth-punching, glib-talking Ali drew fans with his style and confidence, but shed many others because of his anti-war stance and devotion to Islam.
Frazier was the antithesis, a furious package of power who scowled through his fights and spoke little after them. He left school at 13, and lacking Ali's way with words was angered by the way his opponent painted him as an "Uncle Tom", a black man used as a pawn by white society. For his part, Frazier continued to call his opponent "Cassius Clay", the name Ali had left behind with his conversion to Islam.
They met first at Madison Square Garden in 1971, when Frazier won a points decision for the heavyweight title in 15 furious rounds.
Three years later Ali reversed that in a 12-round, non-title scrap before the rivals squared up for the last time, the Thriller in Manila, in October 1975. Boxing historians list this fight high in their order of acclaim, a brutal bout which went right to the final round before an exhausted Frazier, unable to see, was stopped by his trainer from coming out of his corner.
Ali - who had himself been contemplating quitting rather than facing another brutal round - was later candid about "Closest thing to dying that I know of."
Frazier's other two defeats in his professional career came against George Foreman, while he drew his final fight against Floyd Cummings when he came out of retirement, five years after losing his last bout with Foreman.
Frazier's parents worked 4ha of cotton farm and his father Rubin made bootleg liquor to support the family in southern Carolina. One of his purchases was a television and Frazier was enthralled watching Sugar Ray Robinson, Rocky Marciano, Willie Pep and Rocky Graziano work their way through bouts.
Frazier dealt to bullies at school, but lost a scrap with a hog on the family farm when he fell and damaged his left arm. It healed but Frazier was left with a permanently bowed arm, ready for his signature hook.
He broke his left thumb at the 1964 Olympics but won gold and turned pro a year later. Five years later, when the undefeated Ali had the heavyweight title taken from him, Frazier fought Jimmy Ellis and won on a TKO. He then defended his title against Bob Foster.
His second defence was dubbed the Fight of the Century, his first combat with Ali who had returned to the ring after a three-year absence. It was a meeting of two undefeated heavyweight champions.
Frazier won the contest on points but both men ended up in hospital. Ali went straight in to have his jaw mended while Frazier spent weeks recovering from the brutal scrap.
Eventually done with fighting, Frazier ran a gym until ill health forced him to quit.
Seven weeks ago, he was diagnosed with liver cancer then went into hospice care before he was floored for the final time yesterday.
