resentfulness

/rɪˈzɛntfəlnəs/
noun
  1. The quality or state of feeling angry or bitter because you think you have been treated unfairly.
    • Her resentfulness toward her brother grew over the years.
    • He tried to hide his resentfulness, but his tone gave it away.
    • The team's resentfulness about the coach's decision affected their performance.