promising vs unmitigable

promising

adj
  • Showing promise, and likely to develop in a desirable fashion. 

  • a promising young apprentice 

  • Encouraging and inspiring confidence. 

noun
  • The act of making a promise. 

unmitigable

adj
  • Not able to be mitigated or made less severe; not mitigable. 

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