Favored Power Attack( Dragon Compendium)
You can deal more damage to favored enemies.
Power Attack (PH) , Base attack bonus +4, Favored Enemy,
Chose one of your favored enemies. When you use the Power Attack feat against that favored enemy, you may subtract a number from your melee attack rolls and add twice that number to your melee damage rolls. If you are using a two-handed weapon, add 3 times the number. The normal restrictions of the Power Attack feat apply.