Set the options to 9 credits, 5 fire things, and you must be playing with a light gun. Set the light-gun to auto-fire so that if you hold the trigger you will fire more bullets faster. You can defeat the giant opponent easily. . With the four legged monster, you must have very good aim for the full effect of the bullets from the gun. The final silver Boss is the most difficult. Shoot the blades once and they will disappear, Shoot the lighting once and it will also disappear. When he turns brass just keep shooting and he will eventually die.