The phrase "unifying factor" means something that brings people or things together, or connects them, regardless of their differences or conflicts. Full definition
He's the single unifying factor in bringing together so many discrete movie franchises, and Josh Brolin imbues a CGI character who's so ridiculous - looking he's been a meme all winter with surprising humanity. (theringer.com)
If there is one common, unifying factor for most 20 - somethings, it is this: they all have goals. (sun-sentinel.com)
The far right has figured out that the only unifying factor they have is God and guns, so religion has now seeped back into politics. (religion.blogs.cnn.com)