Possible Clues:

• Affliction
• Bugbear, bête noire
• 'You are the ___ of my existence'
• Masked Batman nemesis
• Thorn in your side
• Bête noire; something, or one, that causes destruction
• Water, for the Wicked Witch of the West
• 2012 Batman film villain
• Cause of ruination
• Batman foe who gains superhuman strength by taking Venom