It is the fact that the sins can take over a life that makes them so deadly (at least in a this-wordly sense). To be in the grip of a vice, like Pride, is to be misfit for happiness.
One difference between Pride and Envy is that whereas Pride is typically invisible and hides from us, Envy is not typically invisible, does not hide from us. (Although we try to hide it from others.) We might put the point like this: Pride typically eludes introspection; envy typically does not.
This is an important point. Let me add to it. We can be Proud and not know it, even in cases where we are not guilty of willful self-deception. It is just hard to recognize our Pride. But if we are Envious and do not know it, I think we are willfully self-deceived. In other words, we are actively hiding our Envy from ourselves; after all, it, unlike Pride, does not hide on its own. Envy is not hard to recognize unless we are working to hide it from ourselves. Of course, we can try to hide our Pride, too, if we recognize it. But often we do not have to do that. Pride hides itself. (We do not typically come to know we are Proud by introspection. We come to know it typically as what the philosopher, Arthur Schopenhauer, called "acquired character". That means we come to know it in ourselves by watching ourselves as we might watch a third person, and noting, observing, the sorts of things we do and say.)
