There are many professional boxers who died during their career boxing. For example, Karlo Maquinto, Tosh Powell and Becky Zerlentes all passed away during their boxing match or shortly thereafter due to injuries sustained.
Muhammad Ali had 37 wins by knockout throughout his entire career. There are a variety of forms of professional boxing so the question is not specific enough. For this to be better it should state the weight and not just a general comment.