Doesn't sound good. There are some troubleshooting / reapir options to try, including reverting to your previous windows version, which is the option that I personally would do initially, where I would then uninstall McAfee before attempting to perform another Win 10 installation.
If you can start to the Win 10 logon screen, in the bottom right-hand corner of the screen you will see a 'wheel/power-off' type icon which if you click it will display 3 options, one which is 'Restart'.
If you hold down the keyboard 'Shift' key and click 'restart', then keep holding down the pressed 'shift' key, Windows will reboot into a 'Choose Option' screen. One of those options displayed is 'Troubleshoot'.
Click 'Troubleshoot' and you can then try either 'System Restore' option to revert back to a previous Windows 10 restore point, or the other to try is attempt 'Start-Up' repair.
A third option is to select 'Reset this PC' from the 'Troubleshoot' Screen. With that option it should give you the opportunity to return to your previous Windows Version, as long as it is not 30 days passed since you upgraded to Win 10.
Hope that helps.