Death is natural in the sense that to die is to conform to the ordinary course of living things in nature . For a diabetic to die from lack of insulin would be natural. It would be unnatural for a diabetic to inject natural or synthetic insulin, since injections are not natural. Rotting wood on your porch is natural in the sense that you have not used anything artificial to protect it. The smell of rotting garbage is natural.
Some people are apparently natural born killers.
Squishing bugs and kicking cats is natural for some people, in the sense that they do such things spontaneously, without reflecting on their actions. Nudity is the only natural state for animals, even humans. All clothing is artificial , that is, not natural . So are the fillings in your teeth. So is all make-up and jewelry.