Which team is the Royals' biggest rival?

We live in an age where the Royals are good and teams dislike them. This is a strange age indeed.

The Boston Red Sox and the New York Yankees.  The Chicago Cubs and the St. Louis Cardinals.  Michigan and Ohio State.  The Baltimore Ravens and the Pittsburgh Steelers.  Coke and Pepsi. These are just a few of the well-known rivalries in the sports world, rivarlies which attract significant national attention.  Rivalries exist for most teams, actually, even if the national media does not focus on them.  Really, though, you only hear the word 'rivalry' in a sports context anymore.  Stetson and Valerie from marketing do not have a 'rivalry.' They're probably just bored and don't like how the other…