After the initial cutscene, get into a taxi or drive to the border between Dukes and Broker. Jump onto Adam Dimayev's property and go to the right of the compound. Dimayev himself starts out in a booth with a window near the entrance. If you wish, you may kill him here, although you will still have to finish off the other goons as normal. However, that if you take this route, the guard before where you would otherwise face Dimayev (the one with the pistol) will, once he is the only one left, drop his pistol and attempt to surrender. You may then choose whether to kill him or leave and let him live.
If you fail to, or opt not to, eliminate Dimayev in the booth, he will flee to the roof of the small building on the second tier of the compound. Gain cover behind a car or dumpster and kill all the goons on the first tier. Climb the ladder to get to the second tier. Kill the guards here. Get to the roof Dimayev is on by climbing the shipping containers near it. Kill Dimayev and Niko will automatically phone United Liberty Paper and tell him that he "served his purpose".