Which part of the electromagnetic spectrum transfers the most energy?

Any amount of energy, large or small, can be carried aboard any electromagnetic signal,

long wavelength or short.

The higher the frequency is (shorter the wavelength), the larger is the energy per

each "grain" or "quantum" or "photon" of it. But you can always make the beam

carry as much energy as you want it to, by simply launching more of those. That

just means a higher-power radio transmitter, brighter flashlight, or more-intense

X-ray machine.