Related Clues:

• Bizarro, to Superman
• A McCoy, to a Hatfield
• One to go up against
• Axis powers, to the Allies
• Someone to keep closer
• One against another
• Adversary in war
• Opposing military force
• "An ___ of the People" (Ibsen)
• Axis, once
• The other army
• No proponent
• Scarecrow, to Batman
• One to counter
• Foe hiding, in a way, in the puzzle's four longest answers