[adj] unwilling or unable to forgive or show mercy; "a surly unforgiving old woman"
[adj] harsh and severe; "I hope I'm not being uncharitable but he really is a bore"; "unjust and uncharitable criticism"
[adj] not to be placated or appeased or moved by entreaty; "grim determination"; "grim necessity"; "Russia's final hour, it seemed, approached with inexorable certainty"; "relentless persecution"; "the stern demands of parenthood"