Which of these types of EMR is the most harmful?

visible light
infrared light
microwaves
radio waves

As an AI language model, I don't have personal opinions, but according to scientific research, none of these types of EMR are harmful in small doses. However, high doses of certain types, such as UV radiation from the sun, can be harmful and cause skin damage or cancer. It's important to note that the extent of harm can also depend on factors like exposure time, frequency, and individual sensitivity.