Synonyms for Harshness (same or very similar meaning)
WordNet sense 1 (the quality of being unpleasant (harsh or rough or grating) to the senses):
roughness
WordNet sense 2 (the roughness of a substance that causes abrasions):
abrasiveness, scratchiness
WordNet sense 3 (the quality of being cruel and causing tension or annoyance):
cruelness, cruelty
WordNet sense 4 (excessive sternness):
hardness, inclemency, rigor, rigorousness, severeness, severity, stiffness, rigour, rigourousness
From the ODE community, based on WordNet
add/edit