Well, i've a few pointers here. First off, the setting should fit the concept. This pose shouldn't really take place in such a brightly-lit place, it's not fitting at all. It'd be more fitting in a darker place, like Ravenholm. Secondly, it should probably be a bit more dramatic/suspenseful. Perhaps if the Hunter was leaping towards him from behind, and not climbing up the building, it'd have a bit more energy, whereas if it was secluded in the shadows, ready to pounce, it'd add more suspense.
That's all I gotta say: use appropriate setting for the concept, and give it more of a dramatic/suspenseful edge.
The setting i used was because the "First Week". So the world wasn't that dark yet.
That citizen guy looks like as if he's falling with his hands tied up behind his back. The Hunter seems to be very well posed, but on the other hand looks like he's climbing with his feet. And avoid using bloom.
Also, if you want to use gm_bigcity that badly, try doing the pose in a shady part of the city. Even L4D2 did this by not making the places too bright.
I wanted to make the picture darker in Paint.net,but i only really screwed up. Thanks for the help on the posing,but what do you mean with "bloom"?