cruelty vs oppression

cruelty

noun
  • A cruel act. 

  • An indifference to suffering or pleasure in inflicting suffering. 

oppression

noun
  • The exercise of authority or power in a burdensome, cruel, or unjust manner. 

  • The act of oppressing, or the state of being oppressed. 

  • A feeling of being oppressed. 

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