unforgiving

/ˌʌnfərˈɡɪvɪŋ/
adjective
  1. Not willing to forgive or show mercy; harsh or severe.
    • My grandfather was an unforgiving man who held grudges for years.
    • The teacher was unforgiving of any mistakes on the math test.
    • An unforgiving boss can make the workplace very stressful.
  2. Describing a difficult or dangerous environment that offers no mercy or second chances.
    • The desert is an unforgiving place with extreme heat and little water.
    • The ocean can be unforgiving, with sudden storms and strong currents.
    • Mountain climbing in winter is unforgiving for those who are not prepared.