It was funny, because a lot of what Mary did - killing that woman, but also telling Cas to hurt the vet - was stuff that Sam and Dean do more now, but agonised over for a really long time. Sam in particular.

I think Samuel would have definitely been the reason Mary is like that. I'm thinking John Winchester was one thing as a hunter - Samuel would've been so much more intense. Especially if the Campbells have been hunting since way back, and he was raised in the life himself.

It's possible, of course, that Dean would've been a lot more ruthless as a hunter if it wasn't for Sam. He's the one who has always seen the shades of grey. And I can't help but wonder if that will put them at odds. Because Mary and John would probably be similar as hunters, as is Dean. Sam, though...