Without damaging the paint? You are asking for a lot but the only way I see doing it is to get a body clamp.
Or make something that would do the same like two strips of 1/4" thick flat stock that you could clamp together with a bolt hole thru both.
You clamp the bottom of the fender with a little piece of flat stock on the back side as thick as that fold of metal so you don't crush it. In other words this clamp would be grabbing right where the spot welds are only. You then pull down on this clamp and pull the damage out. You would then only have a little work right along that pinch weld to clean up and spot paint.