Which movie had the most disappointing domestic box office run of Summer 2011?

[Reasonable]

Empirically from your list it has to be Conan given it's probably not even going to cover its production cost domestically and is likely to struggle internationally.

I think in terms of potential expectations you could argue for Green Lantern - although personally I thought it would struggle as the property just isn't know. In fact, I expect, looking at Captain America, to see more of these comic book adaptions of lesser known properties perform only adequately or a little better domestically and to struggle to connect internationally.