I taught pre-K back in the 80's. I met one kid that totally unnerved me every day. He would plot and plan outside and finish by looking me in the eye and saying, "And you can't stop me." LONG STARE.
Then this past year, a friend's 10 year old granddaughter came to visit her. This kid chased her older brother around with a long machete looking knife screaming, "I'm going to change your life."
Those two were the worst ever.