Active corners can't be hidden by command line. Classic Start Menu must be running for them to be disabled. On Windows 8, Microsoft introduced a delay at startup for desktop programs which makes all of them start late. That is why if you uninstall Classic Shell and use a portable installation, it will always start late with some delay even if you place it in the startup folder. Inrstall it so it will try to load faster at startup using faster methods.
You can also use Winaero's Skip Metro Suite to disable hot corners. It completely kills the active corners at startup, even inside Metro but doesn't require itself to be running.
On Windows 8.1, you can try Winaero Charms Killer:
http://winaero.com/comment.php?comment.news.219