to be dead wrong about something or someone 大错特错

英文释义

(SLANG) To be completely mistaken about something or someone.

例句

At first I thought the shy new sales representative would never succeed, but during her first year she made the most sales of anyone in our company, and I knew I was dead wrong about her.

起初，我以为那位腼腆的新销售代表根本不会成功，然而她在第一年里完成的销售额公司无人能比，我这才知道当初对她的看法大错特错了。