Related Clues:

• Hatfields and McCoys, e.g
• Two-Face and the Riddler, to Batman
• Harvard and Yale, e.g
• Airport area overlooks a royal 1 across and 10?
• Opposing sides
• Certainly not friends
• Celtic and Rangers are old ones
• Competitors, challengers
• Two sides of a certain triangle
• Causes of destruction
• Downfalls
• Opposing contestants
• Target and Walmart, e.g
• Two teams playing the same sport in the same league in the same town, most likely
• The Jedi and the Sith, e.g