There was a time when Muhammad Ali taunted Joe Frazier relentlessly, called him ugly and challenged his manhood.
After his old rival died Monday night, Ali had nothing but kind words for Smokin' Joe.
"The world has lost a great champion. I will always remember Joe with respect and admiration," Ali said in a short statement. "My sympathy goes out to his family and loved ones."
He and Ali will be linked forever, both heavyweight champions and bitter enemies in the boxing ring who squared off in three epic fights from 1971-75.
Frazier won the first one at Madison Square Garden in the Fight of the Century. Ali took the last two, cementing his legend as The Greatest.
Outside the ring, Ali called Frazier a gorilla and mocked him as an Uncle Tom. Between the ropes, they nearly fought to the death in the Thrilla in Manila.
Those became the most poignant and defining moments of Frazier's fantastic career. But he also was the only American fighter to win a gold medal in the 1964 Olympics in Tokyo. He was the heavyweight champ from February 1970 to January 1973, an era when that crown truly meant something. He was beloved as an adopted son of Philadelphia, embodying the city's blue-collar grit.
And when the last round of his final fight ended Monday night, reaction to Frazier's death poured in from every corner of the sports world.
"Good night Joe Frazier. I love you dear friend," former heavyweight champion George Foreman, who stopped Frazier to win the title, posted to his Twitter account.
WBO welterweight champion Manny Pacquiao said boxing lost "a great champion" and "a great ambassador."
And it wasn't only other boxers who were touched by Frazier. Tennis star Serena Williams called him an icon and a pioneer.
"Inspiring and loved. Your presence will be missed," she tweeted.
Don King, who promoted the steamy fight in the Philippines that became known as the Thrilla in Manila, was described by a spokesman as too upset to talk about Frazier's death.
WBC light heavyweight champion Bernard Hopkins, a fellow Philadelphia fighter, said Frazier was so big in the city that he should have his own statue, like the fictional Rocky character.
"There's no way in the world you should come to Philadelphia and not recognize who Joe Frazier is. It's the perfect time to build the biggest statue in appreciation for all the heart and love he gave to Philadelphia," Hopkins said. "It's just to say how we regret when it's not there to touch and see. We didn't realize we had a super special person amongst us that we all in a way took for granted. I said this when he was living, I say this now. That's the only thing."
Bob Arum, who once promoted Ali, said the famous bout in the Philippines was "the greatest fight in the history of boxing."
"Joe Frazier should be remembered as one of the greatest fighters of all time and a real man. He's a guy that stood up for himself. He didn't compromise and always gave 100 percent in the ring. There was never a fight in the ring where Joe didn't give 100 percent," Arum said.
Vitali and Wladimir Klitschko, who hold all the major heavyweight belts, paid respect to Frazier on Tuesday.
"My brother and I are very sad about the death of Joe Frazier," said Vitali Klitschko, the elder of the two brothers and the WBC champion. "He was one of the really great heavyweights. He was a great champion and Joe did a lot for the sport of boxing through his social engagements."
Wladimir Klitschko is the WBA, IBF and WBO heavyweight champion.
Former German heavyweight Axel Schulz also praised Frazier.
"He marked the gigantic era of heavyweight in the 1970s. The news made me incredibly sad," Schulz told the German news agency dapd. "I was shocked by how fast it all went."