Harshness, bitterness, or severity
Sourness of taste, with bitterness and astringency, like that of unripe fruit.
Something harsh (e.g. a remark, act or experience).
Tact and subtle skill in dealing with people so as to avoid or settle hostility.
The art and practice of conducting international relations by negotiating alliances, treaties, agreements etc., bilaterally or multilaterally, between states and sometimes international organizations, or even between polities with varying status, such as those of monarchs and their princely vassals.