From unpleasant + -ness.

• IPA: /ʌnˈplɛz.ənt.nəs/

unpleasantness (uncountable)

1. (uncountable) The property of being unpleasant or disagreeable.
2. (countable) An unpleasant behaviour, occurrence, etc.
   • 1814 May 9, [Jane Austen], chapter XVI, in Mansfield Park: […], volume I, London: […] [George Sidney] for T[homas] Egerton, […], →OCLC ↗, page 322 ↗:

     Perhaps you are not so much aware as I am, of the mischief that may, of the unpleasantnesses that must, arise from a young man’s being received in this manner—domesticated among us—authorized to come at all hours—and placed suddenly on a footing which must do away all restraints.

• pleasantness

• German: Unannehmlichkeit, Unangenehmheit
• Italian: spiacevolezza, disaccordo
• Russian: неприя́тность