Yes, once opponent was just pushed and fall with head on pub's floor, he died in emergency room before delivered to intensive care unit.
I sometimes think also about sports fans, they think, that they are experts, what could achieve KO, what no. This punch can deliver KO, this punch not.
For rexample, once guy delivered me on ground with punch, however this not affected my ability or health, just because stance and in general physics. He was beaten after this so hard, that was not able to continue next round.
Different example; precise jab ignited white light, all world become just white universe for about 0,5 seconds. I was not on ground and continued like nothing happened. Sometimes i still feel this jab when nordic winter and long time on street.
Despite advantage in scored points and good condition, i gave up this bout, not continued next round. Why? Not paid, amateur bout in low level competition. Next shoot in head for free? Why if he was better if managed to do this? To entertain people for free?