User blog comment:Epakrios/Plot holes/@comment-207.126.210.191-20140122184549/@comment-11331875-20140123225426

Yeah, I was disappointed that the archangels weren't the ones who killed them for that exact reason, FTWinchester. It makes sense, though--the archangels never went out of their way to kill demons like Lilith and Azazel, so their specifically going after the Knights seemed off, and Abaddon seemed vulnerable to even low-grade angels and angel swords in "Devil May Care", so the archangels probably wouldn't have been needed to be called in to kill them. It certainly diminishes the badassery of the Knights and thus the threat Abaddon poses, though, so I wish they'd stuck with the Knights getting killed by archangels.

Also, with regards to the First Blade and stuff--correct me if I'm wrong, but wasn't Crowley the one who said that archangels used the Blade to kill the Knights? As in, "lying about who killed the Knights in the first place" Crowley? The archangels' ability to kill the Knights was never tested in-universe because the archangels never bothered to go after them, but every indication of the archangels' power against other creatures would strongly imply that they could kill Knights without the First Blade. I know that press releases described it as the only sword that could kill Abaddon, but press releases say a lot of stuff to make whatever they're talking about more exciting/dramatic. "Devil May Care" implied that Abaddon could be killed with an angel blade or simply by a regular angel. That alone would imply that archangels, and their blades, in turn could kill Knights. That Dean and Crowley are going to such lengths to get the First Blade to kill Abaddon without even trying to kill her with the angel blades they already have is either because A.) the blades wouldn't work (unlikely), B.) the plot is requiring them to go to these lengths so that Dean has to work with Crowley again and get the Mark of Cain (probably the truth, but not a good in-universe explanation), or C.) they're afraid to risk the angel blades not working if they attack her with them, since she might survive and kill them (what I choose to believe to explain their behavior).