sternest

1. of a stern or strict bearing or demeanor; forbidding in aspectExamples: "an austere expression"; "a stern face"Synonyms: austere, stern

2. not to be placated or appeased or moved by entreatyExamples: "grim determination"; "grim necessity"; "Russia's final hour, it seemed, approached with inexorable certainty"Synonyms: grim, inexorable, relentless, stern, unappeasable, unforgiving, unrelenting

3. severe and unremitting in making demandsExamples: "an exacting instructor"; "a stern disciplinarian"; "strict standards"Synonyms: exacting, stern, strict

4. severely simpleExamples: "a stark interior"Synonyms: austere, severe, stark, stern