Vindictive, perhaps, but also fundamentally protective. Revenge may be frowned upon, viewed as morally destitute, papered over with platitudes about living well. But the urge to extract a pound of flesh, researchers find, is primed in the genes.

1 An Eye For An Eye or Give The Other Cheek

Chapter 2. Bully

Chapter 3. Coworker

Chapter 4. BOSS

Chapter 5. Neighbors

Chapter 6. Parents

Chapter 7. Narcissist Friend

Chapter 8. Relationships

Chapter 9. Ex Boy & Girl friend

Chapter 10. Children

Chapter 11. In laws

Chapter 12. Spouse / Marriage

Chapter 13. Online Good Samaritan

Chapter 14. Fake Gurus & Mentors

Chapter 15. Haters