It could be a toss up depending on the era. But if we go to the greatest pioneer, ageless pioneer I might say,Cliff 'Magic' thomas, he is arguably the greatest kickboxer for an extended time. He was a 20-1 underdog back in 1980 to Gordon Franks and blew him away in 3 for his first PKA world title. He then beat eight top contenders and former world champions or champions, especially his superb knockout of Paul Vizzio on NBC and ESPN and his becoming the first PKA Kickboxer to hold two titles simultaneously when he destroyed Light Welterweight ChampionTommy Williams in a racially tense atmosphere. Cliff would go on to be the first to hold two, three and four titles in the PKA and when if folded just picked up where he left off and grabbed a 6th. After retirment of sorts, he came back at age 45 to win a 6th and 7th under KICK. Overall, 7 world titles in 5 weight divisions. He never ducked anybody. And he was never officially down and never beat up. As for Urquidez, yeah, he is Top Gun except that Cliff's stablemate, Billye Jackson, defeated him in Florida. It wasn't a world championship and Benny had to agree to PKA rules. But to make the question mute, Cliff offered to fight Urquidez and since they weren't sure if Cliff was still in great shape, they first told him to fight a stablemate named Cunningham. Cliff showed up and they got a doctor quack to say that Cliff still had heart problems. Ho Ho!! Cliff was cut like a diamond. And he was born with a hole in his heart the size of a silver dollar and not expected to even live to age 13 or 14. Surprise! Surprise! Back in Texas, Cliff's physical was A-OK!! So, the world missed out on a whale of a match up. Never happened. Cliff knocked out some 56 fighters, mostly champions or ranked opponents, in over 70 bouts over twenty three years. He only lost six bouts (Some only 5 rounders) and was never in trouble in any fight. He was a champion in 1980 and he was a champion in 2002 and 03. Most famous kickboxers had hung 'em up by then. Bottom line: it is difficult to name the greatest kickboxer just as it is to name the greatest boxer of all time. And there are so many disciplines. But since we all get a swing at it, I'm homering for Cliff 'Magic' Thomas. His website is magicthomas.com and his book is 'Magic! Magic! Magic!.