Let's say you're reading through your favorite Fan Fiction website and one day, you decide to read some stories set in your favorite fandom. New student joins the school, ho hum... wait, did the main villain just step down after one snippy remark by her? That's not right... hey, I thought he already had a girlfriend! Wait a second, did the evil miners all turn themselves in to the police after she had a talk with their leader? Who is this character and why is the whole world bending to her will? Congratulations, you've just met Black Hole Sue. No examples, please. This only defines the term.