Sister Michael!! She was my absolute favorite, though I loved pretty much everyone, even in their meaner moments--the show toes a pretty fine line between likably unlikable and just plain unlikable sometimes, but there's a warmth and humanity to it, especially in the last episode, that kept me going. It shines through in a lot of the little details, too, like the fact that most of Erin's family lives cramped together in one house but makes it work (even if there is a lot of sniping involved), and that they're so quick to take Claire and Michelle and James on the camping trip with them. There's a real heart to it, which I think helps undercut some of the iffier parts, at least for me.