lenient vs unrelenting

lenient

noun
  • A lenitive; an emollient. 

adj
  • Lax; not strict; tolerant of dissent or deviation 

unrelenting

adj
  • Having no pity; not being or becoming lenient, mild, gentle, or merciful 

  • Not relenting; not yielding in strength, severity, or determination. 

How often have the words lenient and unrelenting occurred in a corpus of books? (source: Google Ngram Viewer )