We've seen how the contrast is increased where the slope of the curve is steeper. Click and hold in the image window and move the curser around the subject, and make a mental note of the approximate parts of the curve the marker slides around. Steepen the slope of that part and you will gain a great deal. Once placed, the points remain moveable. A little thought will help you realize that there is no such thing as a curve apart from an image, and no such thing as a generic curve.
Every image is unique, and so is every curve.