It would be interesting to find out which fighter stopped most fighters who never were stopped before or after. I know Louis has a bunch.
Braddock was never stopped either, not by a knockout anyway. As for Liston, he was knocked out by Martin.
Dempsey-Brennan I, Dempsey-Miske III, Dempsey-Willard, Dempsey-Battling Levinski. I checked out Cuevas on boxwreck, and according to them, Pipinio only did this to Espada, Weston, Clark and Bravo. Campanino apparently had previously retired between rounds against Osvaldo Piazza with a shoulder injury in a match he was winning handily, but when the bell rang to start the second round, the referee counted to ten and then declared a knockout win for Piazza. If Campanino's name is accepted in addition to the other four, then that's still only five names on his resume. (At least Dempsey kayoed some HOFers and potential HOFers.) It doesn't matter how hard somebody hits without the delivery system of a Louis or Hearns. This is one of those where some good research really needs to be done. (Lately, I've just been way too stuck in "Dempsey gear," but that's the sort of thing which happens when currently reading up on a particular boxer. If I was happening to be reading Skahan's biography of Marciano, then my answers would be all about Rocky, and so forth. Last year, it would have been all about Mickey Walker, thanks to his autobigraphy.)
Dempsey was the only one to stop Miske in over a 100 fights, the first to stop Brennan in over 50 fights, and the first to stop Levinsky in over 300 fights overall he had(Levinsky was only stopped three times, the other ones outside of Dempsey near the end of his carrier).