Willie Pep
Willie Pep is believed to be one of the quickest and most durable fighters in boxing history. His number of fights is huge, considering the era in which he fought.
Pep won his first 62 professional bouts and was the dominant featherweight fighter of his, and really any, era, holding the title until losing just his second bout against Sandy Saddler in 1948. Pep would avenge the defeat in a rematch and regain his title.
Overall, Pep went 1-3 against Saddler, but dominated virtually every other fighter in his division during this era, leading many to conclude that he is amongst the top fighters in history.