agony vs unhappiness

agony

noun
  • Paroxysm of joy; keen emotion. 

  • Extreme pain. 

  • Violent contest or striving. 

  • The sufferings of Jesus Christ in the garden of Gethsemane. 

  • The last struggle of life; death struggle. 

unhappiness

noun
  • The feeling of not being happy 

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