Once you have completed Dead Rising 3, there will be a post-credits sequence where you chase General Hemlock around the city. As soon as the cutscene finishes, hop off of the roof and grab the assault rifles from the nearby gun shop if you do not have any on you. Ignore the King Zombies entirely to ensure that a lot of droids come out of the ship. The ship will then move from Ingleton to Central City, then to Almuda and then to Sunset Hills. Once you've destroyed the 60th droid, a cutscene will happen and then the final boss battle will ensue. For this fight against General Hemlock, you will want to stay on the platform with him. Keep a medium distance between you and him; if you're too close, he will kick and punch you... if you're too far, he will shoot you and throw grenades at you. Guns are best for this battle, and there are a few around the immediate area. If you run out of ammo, you can always rush him and get off a few quick attacks before rolling away.