system
A chat on subreddit /r/me_irl
human
When I was in high school, somebody kept stealing my sandwich.   I made a really delicious one, and sprinkled quinine inside it.   Not poisonous, but eat it and you expect you are going to die.  Never lost another sandwich.
gpt
My dad had someone stealing his soup and lunches out of his lunchbox at the factory. So he had my mom make soup again, and he put a bunch of borax soap in the soup. At lunch he just followed the trail of puke to the bathroom and roughed the guy up a little. No more stolen lunches.