Hello,
Avast SecureLine VPN is a standalone application. It isn't part of Avast Mac Security but Avast Mac Security has an ability to download it and install from our update servers.
In order to reinstall Avast SecureLine VPN, delete folders /Applications/AvastSecureLine.app and /Library/Application Support/AvastSecureLine if exist and download the installer from
https://www.avast.com/secureline-vpn#macThe supported ways of the product uninstallation are "Uninstall" item in the application's File menu, uninstaller application bundled inside the application bundle or drag&drop to the trash (LaunchD job runs an uninstallation script on the background ).
Best regards,
Martin
P.S. If you have removed Avast Mac Security by the AppCleaner as well, it is in pretty undefined state. I would recommend to download Avast Mac Security installer from
https://www.avast.com/free-mac-security and clean the product remainders using an uninstaller attached to DMG. Than you can install the application again if you like to.