Related Clues:

• One to counter
• Traditional foe
• Ill-wisher
• Source of conflict
• Hatfield, to a McCoy
• Sentry's classification
• Frenemy, maybe
• "Who goes there, friend or ___?"
• Cassius, to Caesar
• Monopolist's lack
• Grant, to Lee
• Mudslinging target
• Them, often
• Adversary or foe
• Am archaic enemy