You must smash about 30 to 35 buildings in the same area. Use the following tricks to make this much easier, but it will still require plenty of patience. Go to the southern-most area of the Financial district where the building are rather large. First, take the buildings near the top subway and go east. When one row is finished, select the next one below (south) and continue:
-Focus on the building. Eventually mechs will swarm around you. Pound it four or five times and jump. -Land several punches on the building from the air. The repeated punching refills your energy. -Pound the corners of the building and the bottom as long as possible. When the entire building falls, it smashes even the ground floor. The standard ground slam does more damage at the bottom. The handclap does more damage sideways. -It is not necessary to smash the ground level stores if the rest of the building is dust. -Take a car and make steel fists. They will last rather long if you use standard punches. -Be grateful for everything that shoots. Run alongside the building if they shoot at you. This will take it down faster. -Use rage only to fill energy because fully charged ground slams or handclaps almost drains the rage meter. -If cornered, jump and find a new pounding place. -Do not worry if you get a notice of U-foes in the area. As long as you do not take out enemies, they will not attack. Warehouses do not need to be smashed; only buildings with windows.