He delivered a knockout blow to all of his rivals.他打昏了所有的对手。High interest rates have been a knockout blow to the business.高利率对该企业构成了致命打击。Already out of training, the latest illness has dealt her hopes of a gold medal a knockout blow.她本就缺乏训练，最近患病更给她夺金的希望以致命的打击。