There aren't really many Kilrain discussion threads so here's one. How highly do you rate Kilrain? He was arguably a top 3 heavyweight at his peak, with wins over George Godfrey, Frank Harold, and drew with English HW Jem Smith. He also famously went 76 with Sullivan, although it was a beating.
Guys in those days had to have unreal pain thresholds to be able to take that much punishment. Arturo Gatti? Yeah his courage and pain threshold (and power!) are legendary but he would be a baby fighting 12 rounds compared to these guys who went 76! Even if they sometimes fought one minute rounds, it was still about 2 hours of constant hitting each other! One of his fights went 106 rounds before being declared a no contest due to darkness. That fight had one minute rounds, and so that amounted to 106 minutes, an hour and 46 minutes! From the Wikipedia article which I did not write, he was an incredibly brave and skilled fighter with decent power and who was one of the top Heavyweights of his day.
He was perhaps the 2nd or 3rd of his day. But as with Sullivan it is kinda of hard to rank em in a all time sense with lack of footage.