Possible Clues:

• "You're going down!"
• "Challenge accepted!"
• "You just made yourself an enemy"
• "Now you'd better watch out!"
• 'NOW you've crossed the line!'
• “Now you’ve messed with the wrong person!”
• Verbal equivalent of picking up the gauntlet
• “You’re going down!”
• (Cracks knuckles) "Challenge accepted!"
• 'You better believe I'll fight!'