unmerciful
/ʌnˈmɜr.sɪ.fəl/Definitions
1. adjective
showing no mercy; cruel or harsh in one’s judgments or actions
“The unmerciful landlord raised the rent by 20% without warning.”
2. adverb
in a way that shows no mercy; cruelly or harshly
“She was treated unmercifully by her cruel stepmother.”