Like that one time when my brother got upset that I ate the last of the ice cream (maybe I took it from him? Small detail really) and he chased me down the hall and knocked me down and sat on me and proceeded to STRANGLE me. Yes. Thats right, he choked me. Hands around the neck, head knocking back and forth. Me going "ugh, ugh, ugh!" My sister crying in the corner. It was lovely.
One time my Grandpa babysat us and although I have a wonderful grandpa and I love him, somehow we weren't quite meshing that night. I don't remember what he yelled at me for (I'm sure I was completely misunderstood and had done NOTHING wrong) but I DO remember the crying. And making sure that the tears stayed on my cheeks as I went to bed so that my parents could see them when they got home that night and feel AWFUL that their sweet daughter had been so mistreated.
I started babysitting when I was twelve and believe you me, I made LOTS of mistakes. I'm not going to share them because I wouldn't want child protective services called, which is why I NEVER want a twelve year old to babysit my kids.