That is one and likely the worst. The second is moving your rig into a place or situation that isn't good for it. I once witnessed a gent pulling another hard stuck from down below him. All the weight was on the front axle and was pulling the rig over to the edge of a ledge that would not be good to go over. He was in park with the brakes on, popped it into reverse since the winch was overpowering the brakes and gently gave it some throttle to try and back away from the edge. He had stopped the winch, but the load was very high and as soon as the torque hit, it broke both front axles nearly simultaneously.
I think I misread your earlier question with my earlier answer.
Leaving the Jeep in park is a big one (at least until it can no longer be considered in park...). So is standing next to the winch with a controller in hand. Recovered vehicle driving over the winch line. Recovered vehicle not helping or "helping" too much. Leaving recovered vehicle in park. Getting out of recovered vehicle when it should have a driver.
The worst is a buddy of mine, he's one of those that just can't decide on which Jeep to work on which day, or which end he wants his winch on, so he has a receiver mounted winch that sticks an extra foot and a half out... He also finds the tightest trails to go down and is always backed into a hill, rock, or tree where he either can't get the winch out of his trunk or can't get it into the receiver. Thankfully his 1/4" ultra reinforced bumpers haven't snapped when he does side pulls with that setup.