Hi,
I have looked at probably most everything that may do this and turn it on (wake timers) in Windows 10. I wake up in the morning and my monitor is back turned on. I physically turn it off when I am done using my desktop. It's a custom built box (i5 4690 16GB, 960 GTX 2Gb, gigabyte mobo Z97 model). I believe it is being turned on from some form of wake timer and avast's nightly system scan which puts a window up on screen to display results of scan.
Only other program that runs nightly is Malwarebytes and I am going to check their forum. I doubt it is that program since it doesn't pop up a window after scan complete (no issues found - and none found with Avast as well). So I am leaning on it being an Avast issue that i haven't tracked down yet.
Any ideas? I've tried all the options I've found online for this as far as I can tell and turned off NIC adapter and keyboard/mouse events and a few others and checked power settings/tweaked things to be off in there as well.
Mike