How do I completely uninstall Virtualbox from macOS? I want to know how to uninstall virtual box correctly. I tried removing it from /Applications, but lots of things were left behind. I don’t want to use an app cleaner tool and would like a complete uninstall process if possible. 

How can I remove the app and reverse the changes it makes when installed?
The correct method to uninstall Virtualbox is to use the official uninstall script that is included on the installation image.  If you don't have the installation image anymore, you can re-download it. Since the program installs many helper scripts outside the /Applications folder, you need to clean those up with the included uninstall tool and not just trash the main app. 

This information is available directly from the project page as well:
https://www.virtualbox.org/manual/ch02.html#install-mac-uninstall