discourager

/dɪˈskɜrɪdʒər/
noun
  1. A person or thing that makes others feel less confident or less willing to do something.
    • A good coach is an encourager, not a discourager.
    • The constant rain was a discourager for anyone planning an outdoor event.
    • He was known as a discourager of new ideas in the office.
Synonyms