That's a knockout and a tasty 1.05 point modifier for you!
While the ordinary course of Challenges in the world of Agent 47 involves killing things (and people) this particular Challenge does not. Unless you consider killing a punching bag as an assassination?
Basically you should scan the horizon until you spot the athletic individual working out with the punching bag that is suspended from a frame on the rooftop terrace of what is presumably his luxury flat. Your objective here is to shoot the punching bag until it falls off of the frame, and then observe the reactions of the man – The Patriot – who is suggestive in his response. Can you guess what he is thinking?
Helping The Patriot learn Vizzini's Lesson
If you are a good shot (and you should be, as after all you ARE the infamous Ghost, Agent 47, a man Interpol is convinced is an amalgamation of a dozen or more other men) you should be able to do this in a single shot. Did you? Watch the video above for a guide to the on-shot-on-err-bag-kill?
By the way, if you shoot him, you fail the Challenge. Do try not to shoot him, right?