The worst thing I can imagine seeing when I open up the administration in a WordPress site is Visual Composer. This plugin is for con-artists to use and pretend to be real website developers. It makes a giant mess of the page. It's used by people that don't know the slightest thing about website development in order for them to portray themselves as web developers.
If your developer used Visual Composer, they're not a developer and you've been ripped off. You can expect your site to load extremely slow first of all. Then, if you need any kind of customizations done later, it will cost double or triple what it would have cost without that 'con-artist extension' because modifications will have to be made to override the Visual Composer code.
Avia is a similar product. Both of these products are EXTREMELY unprofessional. Would you use plexiglass for your physical storefront instead of real glass to save money? That's the same thing you're doing if you hire a developer for cheap and they use these types of plugins on your WordPress site. They are NOT WordPress developers. An elementary school child could have created your website with these types of extensions. Might even look okay, but probably not. Will probably have bugs. And will most definitely not be mobile friendly or ever get indexed in Google mobile search results.
In my opinion, this is the very worst extension ever developed for WordPress.