The threat was Superman's very existence and purpose. I suppose that Lord V's human name could be close to Vendetta...since he showed an image of himself to Clark that was very close to the Guy Fawkes mask
and that was essentially what he was unleashing against Superman.
It's okay if you didn't like or understand what was going on Trekker...at least you gave it a shot
Also as I've mentioned before this entire thing I think was also partial set up for Multiversity later on. You didn't have to understand the references or whatever, but that's my theory since Morrison himself stated that we would see President Superman as a major character in one of the issues (I assume the story that will feature his Earth).