Next time they talk to you (if you even do that) they tell you of misfortune, right after your look befell them. Then they will ask you why did you look at them such way, if they dare ask at all. They might think you will kill them for the rest of their life(some thought that of me). If your look was really powerfull, you would never see them again.
You now see someone you hate. For a long time volcanoes have been brewing in your mind. Perhaps even you have went so overboard as to have let it erupt onto them. Dissatisfaction that the revenge that you had in mind is still brewing. You have imagined this would be, or that. They know you dislike them. You even have made plans to kill them (even in your head). Decency(spelling?) prevents you from springing upon them in public. Your hatred causes you to stare. Feel this down to the bottom of your core. Bring to mind all that you wish to do. If they look at you with all that festering and get any impression of the intent in your mind, they curse themselves with whatever impression they got. An added point is to release it from out of you into them and cast it into them through their eyes.
The eyes are indeed the windows to the soul.