The "Super Hammer" cheat requires 100 kills with the sledgehammer. To easily unlock it, go to dust near the chemical depot that is near the Badlands. Kill a few guards and go back out of the depot. Wait for cars to come by and take them from the civilians and the guerrillas. Form a wall using these cars with only two openings just big enough for people to fit through. Wait for the EDF to start coming in through the holes. Take out the sledgehammer and start bashing in heads. If they start trying to bash the car wall, blow up their cars. You can use the sledgehammer, but it will take awhile. Try using the explosives, because the kills do not have to be consecutive. Keep doing this until you have killed enough EDF.