Facebook page optimization

[measurableROI]

I'm working with a client who is "under attack" by one unhappy customer.  That customer created a Facebook page to share her outrage, and her page is outranking my client's (consistently immediately above his FB page).  I've checked all of the obvious things...

• page name
• page URL
• About section, and all business-related data

He has MANY more "Likes" than she does, makes posts far more frequently (with much better Engagement), references his company name in almost every Post (as she does), and on and on.  My main question is this...  are there one or two factors that seem to have the most impact on how a given FB page ranks?  Thanks for your help, Moz family!