A romantic stalker.
Someone you might see a few times, who then won't accept that you don't want to continue the relationship. Becomes obsessed and intense over you.
In the film Fatal Attraction, married Michael Douglas a has a brief sexual affair with Glenn Close. He ends the affair, and amongst the many deranged actions she takes to get his attention and wreak revenge, is to put his daughter's pet rabbit in a pot on his stove and set it to boil, so that his wife discovered the boiled bunny when they come home after a day out.