Use the Apple recommended method for uninstalling an application:
Hold down the app's icon in Launchpad until all the icons start to jiggle, and then click the app's delete button (X) to uninstall the app.
You can reinstall the app by viewing the App Store Purchases list and clicking the Install button for the app.
Please note there is no uninstaller for Bitdefender Virus Scanner. There is an uninstaller for Bitdefender Antivirus for Mac, which is a different product, not available on the App Store. The uninstaller for Bitdefender Antivirus for Mac does not work with Bitdefender Virus Scanner (the Mac App Store version). To remove Bitdefender Virus Scanner correctly, follow the steps above.