User blog comment:IamJakuhoRaikoben/Chapter 445: The Ugly Fairy, Review./@comment-26451407-20150720022152/@comment-7418318-20150720072044

Now where would that "half of his power" come from?

@Anon: While Face was active, Igneel had the upper hand and was able to knock Acnologia out of the sky. After Face was shut down by the other Dragons Acnologia woke up again and defeated Igneel. I'd say that's a pretty good indication that Acnologia was affected by Face.