Related Clues:

• G.I. Joe and Cobra Commander, e.g
• Some fighting forces
• Hamilton and Burr, notably
• Redcoat, to a Minuteman
• The Hatfields and the McCoys, e.g
• Opponent in Risk or Stratego
• Decepticons, in the Transformers universe
• Some military groups
• Filibustering group, maybe
• North and South Korea, e.g
• Other side in a fight
• Poison Ivy and Mr. Freeze, to Batman
• "World of Warcraft" forces
• "Them," to "us"
• Spider-Man and Doc Ock, e.g