It doesn't work, energy follows thought and it makes no sense to focus it on what you want to avoid. Take or leave.
That being said, the worst I ever saw was the in-house business nonsense I was paid to deal with as a Java consultant. The worst code isn't open source from my experience, subjecting it to public scrutiny would mean suicide for the companies involved.
This matches my experience. Open source projects tend to get the worst parts fixed. It's in-house applications, usually written in VB / Delphi / Java, that have been supported and added to over the past 20 years where the true horrors lie.
As you say, I doubt many businesses would be willing to put this kind of code out there.
That being said, the worst I ever saw was the in-house business nonsense I was paid to deal with as a Java consultant. The worst code isn't open source from my experience, subjecting it to public scrutiny would mean suicide for the companies involved.