The force diagram for a rock swung in a circle at the top and bottom of the circle is shown in the image attached.
The force diagrams at the top and bottom of a circular motion, like swinging a rock on a string, are different. At the top, tension and gravitational force work together toward the center to provide the centripetal force required for circular motion.
At the bottom, more tension is needed to defy gravity and keep the rock moving in a circular motion. The net force is made up of tension and gravitational force.