He was more active than any recent heavyweight champion, and he fought in a record 29 heavyweight championship matches. He defended his title against all comers in four countries on three continents.

He made five successful title defenses in his first reign as champion and an astonishing 18 in his second reign, which covered more than nine years.

Wladimir Klitschko is one of the greatest heavyweights who ever lived even though he had no career-defining victory or seminal moment in the ring.

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He was a guy who presided over one of the worst eras in heavyweight history, when the number of legitimate challengers was few. Yet Klitschko, who announced his retirement Thursday with a 64-5 record, a 25-4 mark in heavyweight title fights and 53 knockouts, was never fully appreciated.

He never ducked anyone but his older brother, Vitali Klitschko, joking that he didn’t want to make his mother cry.

Though Lennox Lewis and Evander Holyfield were in their primes when he won his first heavyweight title belt in 2000, he never got the opportunity to face either man.

He was a brilliant athlete, a magnificently proportioned and conditioned giant of a man. He stood 6 feet, 6 inches with an 81-inch reach and a jab that may have been exceeded in heavyweight history only by Larry Holmes, Muhammad Ali and, perhaps, George Foreman.

He moved like a man much smaller, light on his feet and, thanks to the tutelage of the late, great Emanuel Steward, cut off the ring expertly.

In the short term, he may be known more for three stunning losses – to Ross Puritty in 1998, to Corrie Sanders in 2003 and to Lamon Brewster in 2004 – than for any of his wins. Each was a massive upset that rocked the boxing world and in at least two cases, against Puritty and Brewster, he inexplicably lost his conditioning. He became exhausted in both bouts and was out on his feet when he was finished by men he’d been heavily favored to defeat.

But he re-established himself after the loss to Brewster and reeled off 22 consecutive victories before ending his career with back-to-back losses to Tyson Fury and Anthony Joshua.

For all his greatness in the ring, though, what made Klitschko special was his presence outside of it. He was a man of arts and letters, owner of a doctorate in sports science, a charitable man who tirelessly raised money for children and who fought for human rights around the world.

In 2014, he famously stood shoulder-to-shoulder with his brother, leading anti-government protests in the Ukraine.

He made the world a better place for many with his efforts, standing as a symbol of courage and defiance in the face of overwhelming political power. In that way, he was like Muhammad Ali, one of his idols, who a generation earlier had fought his most important battles far from the boxing ring.

Klitschko is one of the seminal figures in boxing history, because of his success in the ring and his presence outside of it. But there was always a sense of vulnerability to him, and the perception was that this powerfully built man was somehow dainty.

His ability to take a punch was frequently questioned, though he should have answered that charge forever when he defeated Samuel Peter on Sept. 24, 2005, in the bout that may have saved his career.

After losing to Brewster, Klitschko returned to score knockouts in non-title wins over DaVarryl Williamson and Eliseo Castillo. They were safe bouts, though, because Williams and Castillo were small heavyweights – each 30 pounds lighter than him – and didn’t present a serious challenge.

But when he fought Peter, Peter was at the height of his powers and one of the hardest hitters in the sport. Peter was by no means a great fighter, but he unquestionably was one of the hardest hitters of the era. He dropped Klitschko three times, but Klitschko pulled himself off the canvas each time and went on to win a wide decision.

It helped him to rebuild his confidence, which sagged with the losses to Sanders and, particularly Brewster. It remained with him until the end as a 41-year-old facing a far younger opponent in Anthony Joshua.

Joshua stopped Klitschko in the 11th round on April 29 before 90,000 fans in Wembley Stadium in London in what remains the leader for 2017 Fight of the Year and is among the best heavyweight fights in the last quarter century.

He never got the opportunity to fight Lewis, who was the dominant heavyweight of the first half of his career. Klitschko debuted in 1996 and won his first title in 2000, but Lewis retired in 2003 after defeating his brother, Vitali, in a sensational match in Los Angeles.

The lack of that kind of opponent kept Klitschko from being truly embraced by American boxing fans.

The history books, though, will treat him far more kindly than he was in the midst of his career. So much was expected from a guy of his size and athletic ability, and while he delivered – no other heavyweight won as many title bouts as he did – the air of vulnerability that surrounded him led many to discount his talent.

He took seriously his role as champion and used the bully pulpit he gained from the belt to benefit others. In 2002, Klitschko and his brother became ambassadors for the United Nations Educational Scientific and Cultural Organization. He worked tirelessly on its behalf, donating time, money and energy to advancing its mission.

There have been few like Klitschko in the sport, and boxing is greater for having him in its midst for more than 20 years.

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