And the evil grass is...

Orchardgrass.

This is in the backyard.

That's it.

Thanks to my father in law for the tip! It's surprisingly difficult to find good closeup shots of it in a turf grass environment because it's typically grown for hay or a pasture, but I found some good photos here (I also found a good guide for identifying it, but can't find it now).

I feel like I should go back and update all my previous posts now. While I know the lawn contained plenty of tall fescue, I mistook the orchardgrass to be the same thing. Don't get me wrong, I dislike both of them in our lawn, but orchardgrass is the unkillable beast. Non-selective herbicide (like Roundup) and pulling it up are the only way to get rid of it, and pulling it up is as I have found is quite challenging.

Anyway, after two reseedings, selective herbicide applications, and hours and hours of pulling it up by hand, I have mostly eradicated just about all of the tall fescue and orchardgrass from the lawn. I'm sure some that I recently pulled will come back, but needless to say I'll continue pulling it up as long as I can see and move.