I have committed a long list of evil things and on that list are some points of which I assume they were immensely more worse than intended or anticipated. So to find the most regrettable one is almost impossible. In an attempt to compliment someone I made some public remark that backfired since the "compliment" turned into a racist/sexist insult when received and I had no chance to sort it out. I'm still ashamed of it though the double meaning of my wording wasn't obvious to me when I said them.