Lucifer saying his brother called him a freak and a monster--I cannot picture those words coming out of an angel's mouth for the life of me (though I don't doubt Michael did say something similarly provocative), but that's exactly what 'Dean' said to Sam in Lucifer Rising.

And if it turns out that the Michael-Lucifer fight that those words provoked was induced by Zachariah or somebody the same way the Dean-Sam fight was, I will squee so loudly they'll hear me twelve timezones away.