Completely Disable Action Center in Windows 10
1. In Registry Editor, go to following key:
HKEY_CURRENT_USER\Software\Policies\Microsoft\Windows\Explorer
2. In right-side pane, create new DWORD DisableNotificationCenter and set its value to 1
3. Restart, log off or restart Explorer as given here to take effect and it'll completely disable Notifications and Action Center in Windows 10.
If you want to re-enable it, delete the new DWORD DisableNotificationCenter.