"Back home," Michael started, his tone a little derisive. He did want to go back, of course, that was the whole point of trying to behave now, but he was fully aware that it was going to be a colossal shitshow when he made it back. "It seems the strength of the nephilim depends on the strength of the angelic parent. Unless Gabriel has been keeping secrets, which is possible, that abomination is the first nephilim to have been produced by an archangel. That's a level of power the Winchesters should not have access to, not that it has ever stopped them before."
At the time he hadn't truly had the strength to fight Yves on actually killing the anti-christ. He would have been lucky to leave a dent on the abomination, let alone take on the other archangel if he stepped in to stop him. He hadn't believed him about what price would have to be paid in order to kill the abomination, now he was starting to rethink his position. It needed to die, but now Michael might have been willing to accept it would take more than just burning him out.
"Antichrists are supposed to be different, the children of demons as you know, and while I'm sure we can both say a great deal about Lucifer, we can agree that he is still an archangel. If this thing that's here is claiming Lucifer as his father and continues to demonstrate the abilities of an anti-christ then this might all be a touch more serious than I imagined." That meant he would have to do something about it himself, and he would probably need the help of the other archangels there and none of them were likely to be interested at all. Of course, things couldn't be simple, not with the Winchesters so close.
Perhaps he ought to smite the pair of them and Castiel just to keep them out of the way.
"Yves, yes. When this place goes up, and it very well might, you can track him down and shake his hand. His compassion for that thing might doom everyone here in a manner that makes your considerable evil pale in comparison."