In order to beat any boss you have to have a full crew (at least one other gunman, then a bouncer, then a female with acid spray... in order of necessity). At first you can only have one or two henchmen with you, so use a gunman and a then bouncer. Engage the boss's crew outside of his safehouse first and run into the house next to it. Run to the back and use your cover wisely. Before engaging your bouncer lob dynamite at the crew, which should stop in the doorway. One blast will take most of them out. Once you beat the crew (easy) go into the safehouse and move to the middle of the room. Lob a stick of dynamite then sick your entire crew on him. It should drop him in a couple of seconds. Don't pay any attention to any crewmembers as they will die when the boss does.