Tyson by KO seems likely to me, yes I understand that he had some serious medical conditions in his life so far, and when you are a boxer, growing old is not easy. Human body wasn't built for getting punched a million times in a life time, and that's why its tough to be a boxer and grow old, not that it can't happen, but many do have some medical issues. However, we are talking about Jake Paul here, that kid doesn't look like anything compared to Mike Tyson, its not about size, its not about pace, its not even about punching power, its about the fact that Mike grew up to be the best there ever was, so that technical skill and talent doesn't grow old.