Let's answer this question slowly: Did Jack Dempsey have most title fight wins in either of his weight classes?

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Jack Dempsey competed as a heavyweight and a lightheavyweight. Jack Dempsey only had a handful of title defenses as heavyweight champion. Wladimir Klitschko had 25 heavyweight title fight wins. Jack Dempsey did not hold the lightheavyweight title. Dariusz Michalczewski had 23 lightheavyweight title fight wins. So the answer is no.
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