That's Why You Came to Me

In "In the Pale Moonlight," Sisko backhands Garak after learning that he was responsible for the death of the Romulan senator Vreenak, and lands another blow after figuring out that he killed the forger Tolar as well. But, as Garak points out, Sisko came to him in the first place precisely because, having tried everything else, he needed somebody that was willing to do whatever it took if he was actually going to draw the Romulans into the Dominion War.

Example of:
Bad Guys Do the Dirty Work