At the start of the fight, run up to him and start using homing attacks on the Black Volts to get to his eye. When you hit him once, wait until Shadow comes out of spinning from the recoil and straightens up, then attack again. This will minimize your chances of diving to him and getting hurt instead of another homing attack. Continue this as long as possible. When he is in the middle of the street, there will be no Black Volts to bounce on. Instead, run directly under his head, then run away before he creates a shockwave under himself. By doing this, Black Bull will tilt his head down, making it an easy target. When he moves back, repeat. If you get a Gun from Black Arms soldiers, use it, but do not waste it. You will most likely fill your Hero gauge by then. Use it when he is easy to hit, then finish him off. He should not be too hard to defeat.