Like I said before I really don't know a lot about this but I have had a quick look on the wiki page you posted and at the monsters on supernatural and I been thinking about Foxxie, now I know that I already said she is the obvious choice, and the obvious choice isn't always the right one, but what Dragon said about Meg got me thinking about there is a demon in the group. So here's my idea. What if Foxxie was Meg not K-9? Think about it, you got a group of hunters talking about how dangerous and evil ALL demons are. Right in front of a demon who has betrayed her own kind to help the hunters save the world, going out of her way to help members of her group, so it would make sense that she would get a little bit annoyed about everyone talking about how bad demons are like she wasn't even there considering she was trying to help everyone. Plus she would know that there is actually things out there that are more evil and more dangerous than demons. As according to the wiki the Leviathans sound more dangerous than demons because nothing can kill them and god created a supernatural prison for them.
'The Leviathan(s), also called "Chompers", the Old Ones or sometimes Levis for short, were God's very first beasts, and thus pre-date angels, humans, and the soul itself. The beasts proved to be too hungry and destructive, so God created Purgatory and locked them inside. They were inadvertently released when Castiel opened Purgatory and absorbed all the souls inside in order to defeat Raphael.'
Now knowing this and knowing that Lucifer is in the group who is a fallen angel who is in charged with hell and demons, considering Lucifer is known to be very proud and arrogant, there is a small chance that Cordi could be Lucifer because his response to Foxxie, saying they are worse things out there than demons was simply 'There aren't' And assuming that most hunters or at least the experienced ones know about the Leviathans, then Cordi's character would know there are in fact worse things than demons but if he was Lucifer then knowing about the Leviathans wouldn't make a difference because of his pride and arrogance he would believe demons are worse.