You're probably looking for a hitman report, which is something I've been wanting to implement, but just haven't gotten all of the necessary infrastructure into the program for, yet.
But, in the latest beta version (2.6.b5) there is a simplified version of this report (this is not in 2.5.12). On the Stats tab, press the "View" button, then select "Single field view", then select the "Hitman" column. Voila.