My sister was three years younger than me, so I had to be 20-21 when she got her driver's license. After she did, she thought it was funny to follow me around everywhere, just for the sake of annoying and embarrassing me. She was in the middle of a weird total retard phase, where she'd just do the most witless stupid things for no reason. So one day I was driving down a straight road, no other cars around, and my sister was coming the other way. When she recognized my car she thought it'd be hilarious to jerk the wheel back and forth, weaving into my lane, and she was flying too. I started braking, as she was heading straight for me. She nearly lost control of the car, but avoided hitting me by an inch or two at most. As she passed me I saw a look of complete and total retardation on her face that just chilled me to the bone. Her friend, who was in the passenger seat, leaned over and flipped me off with an evil sneer on her face.
When I got home a little later, I went straight to my sister's room, kicked the door open, grabbed her friend by the throat, threw her against the wall and told her if she ever flipped me off again I'd pin her down and break every one of her fingers with a hammer. Then I grabbed my sister by the throat, slapped her across the face twice, and warned her that next time she was just simply going to disappear, and no one would ever know what happened to her. She never pulled that kind of shit again after that. It was the only time where I genuinely felt that violence against women was totally justified.