I just realize and still can't believe how powerful Billie really is. Seriously she can take a single Charmed One, maybe expect Phoebe. And I won't even invoke the 12 Angry Zen episode. There must be a charmed power as powerful as hers in a fight. I nominate Phoebe's empathic gift. However, this relies on who's quickest to the draw as both power activates on a single thought. And whoever stikes first gains the advantage.
Let me know what you'll think. And nominate a Charmed One power that you think can take her and Why.