I thought this was a problem with a mod. But it's not. Because it won't even run with no mods being launched through the .exe or Launcher or via Steam. I get any number of errors. "Access Denied", "You do not have proper permissions to run this application", "Can not find the file, application you may not have administration rights".

Windows 10, logged in as an ADMINISTRATOR (I'm not sure how much more administrative I can be), Fallout 4 is up to date. What gives?

Run Fallout4.exe as administrator?

Is this a clean Windows 10 install or a upgrade from 7/8/8.1?

An administrator user account and running an application in elevated mode (run as admin) aren't the same thing. Also certain file paths, namely Program Files have added security.

Try to do that on the whole folder where Fallout 4 executables are. (or even at the executable in question)

https://www.youtube.com/watch?v=FzmX7ZW6C9Q

Also check your security programs especially Defender it might be blocking access for the game.