The most dangerous EM wave present is the Gamma wave.
They have the highest energy among all electromagnetic waves as they have extremely high value of frequency.
One photon of the gamma rays can break a whole flock of chemical bonds as it passes through a body and then pass through with ease.
Exposure to gamma radiation causes cancer in human.
They can also tear the covalent bonds of the molecules that make up live tissue since they have such high energy as have strong penetration abilities and can do a great deal of harm because of their energies.