unlenient
/ʌnˈlɛniənt/Definitions
1. adjective
not willing to give leniency or to show leniency
“The strict judge was often criticized for being unlenient in her sentencing.”
2. adverb
in a way that is not willing to give leniency or to show leniency
“The police were unlenient in their pursuit of the fleeing suspect.”