Okay, normally, I don't do this kind of thing, but I can not get it out of my head.
Carmilla said the best thing to kill an angel with is to fight for what you love. To fight for something you believe in. And that's what the whole gang does.
Charlie fights for her dream
Vaggie fights for Charlie
Angel and Husk fight for their friends
Lucifer fights for his daughter
Sir Pentious DIED for love and friendship
Guess who doesn't win in their fight?
Alastor can not comprehend dying for friends of all things. He was fighting for power he was fighting for freedom, and he lost his fight.