Related Clues:

• Thumbs-down group
• They aren't behind you
• Combatants
• Some are bitter or sworn
• They're opposed in war
• Foe hiding, in a way, in the puzzle's four longest answers
• Ones to beat
• The bad guys
• Ill-wisher
• The Axis, to the Allies
• Hatfield, to a McCoy
• Allies' antitheses
• They beg to differ
• "Where ignorant __ clash by night": Matthew Arnold
• The FBI, to the mob