unmercy

From Middle English onmerci, unmerci, unmercy; equivalent to un- (“lack or absence of”) +‎ mercy.

unmercy (countable and uncountable, plural unmercies)

1. The lack or absence of mercy; mercilessness.
   • 1870, Octavius Perinchief, Sermons Preached in Memorial Church, Baltimore:

     There is justice and injustice, mercy and unmercy, love and unlove, self and unself, faithfulness and unfaithfulness, the well-being of others and the ill-being of others, the honor of God and the dishonor of God.

• unmerciful