Final answer:
The protagonist, Doug, wants revenge on Ralph because he believes Ralph caused him emotional pain and humiliation during their childhood.
Step-by-step explanation:
The short story 'The Utterly Perfect Murder' by Ray Bradbury tells the story of a man named Doug who wants revenge on a childhood friend named Ralph. Doug believes that Ralph caused him emotional pain and humiliation when they were kids, and he has carried this resentment for many years. His desire for revenge stems from his pent-up anger and the feeling that Ralph deserves to suffer as Doug did.