The bit with the two tallboys at the end of the flooded district in dishonoured.
I've been through dishonoured at least three times now, trying different ways to play it, and this section always annoys me. It's a wide open space. An electrified bridge crosses it, with empty buildings by the side. Thing is, the tallboys will probably spot you even in the buildings because they're...well, tall. Combat with tallboys is possible, but insanely difficult. I don't think i've ever managed to take down two in the same area. They would seem to have a weak point at the back with the highly explosive whale oil tank, but I've never been able to get it to go in one shot. For me, it's always came down to getting as close as possible to the other side, and legging it.
Hell, the entire game kinda gets a downer put on it by the arrival of the tallboys. Ground level cover is no longer a wise option, as one unpredicted movement by a tallboy'll have you spotted as easily as if you were strolling down the street with weapons drawn, thus dulling the main selling point of dishnoured, and the reason I've played it so many times considering I got it under a month ago; The variety of choices in how you play.