The great lightweight Lou Anbers killed an opponent in the ring Tony Scarpati, way before Ambers became champion.
Apollo Creed died in the ring; otherwise, nearly all--even Johnny Owen (7 weeks)--have died days or weeks later. Scarpati died 3 days later. From memory, "Dracula" died about one or two weeks later.
Max Baer usually gets credited with the death of both Frankie Campbell and Earnie Schaff although Schaff died in his bout with Carnera. But I've also heard Max killed a man in sparring anybody know any details?
Yes, Baer does get credited (unfortunately 'credited' IS the right word, because it's usually brought up in the context of discussing Baer's prowess). But it's bull**** really. It was hype and conjecture on the part of the press, I believe. Sure, his beating of Schaaf very possibly contributed to Schaaf's death, but Schaaf had fought a ton of tough guys, in the ring and in the gym, and taken a fair few punches, and any of all of them might have contributed.
Here is a BBC documentary from 2002 where Johnny Owen's Dad goes to meet the fighter in the ring, when his son died. [yt]gjdSt5RJdKs[/yt]
Just a bit of trivia -1) in the 4 months between the Baer fight and the Carnera fight, Schaaf fought 3 more times. 2) His last fight before Carnera he stopped the #3 ranked Stanley Poreda in 6 rounds. 3) Poreda was coming off a win over Tommy Loughran and after his loss to Schaaf he stopped Tom Heeney in 10. 4) In his fight with Baer he did not so much suffer a bad beating as he did a bad KO. He was actually ahead on points and would have won the fight but Baer pulled back a KO but the bell rang ending the fight and he took the decision. It appears Schaaf may have just suffered from a very hard, budy schedule.