grumbler

/ˈɡrʌmblər/
noun
  1. A person who often complains or grumbles.
    • The office grumbler made everyone else feel tired with his endless complaints.
    • Don't be such a grumbler — the weather is actually quite nice today.
    • My uncle is a constant grumbler, always finding something wrong with everything.
Antonyms
What does "grumbler" mean? | whatsthatwordmean | whatsthatwordmean