I think 'unpleasantness' is really the main thing.
A sound can really get on a person's nerves if it's strident. The stridency of a sound can make you cover your ears to avoid hearing it. Likewise, the appearance of a thing can really get on the nerves if it's garish. The garishness of a piece of clothing or a painting, say, can make you avert your gaze to avoid seein
"Unpleasantness' is certainly the first word that came to my mind, too, CJ. However, I thought, with the given selection of word-pairs, 'excessiveness' allowed Jeff to effectively eliminate all the others. If, for instance, 'outrage: anger' had been in the list, 'excessiveness' would not have been a precise enough clue.