detractor
noun
[ dɪˈtraktə ]
• a person who disparages someone or something.
• "the island, say its detractors, has been devoured by development"
Similar:
critic,
disparager,
denigrator,
deprecator,
belittler,
attacker,
censurer,
fault-finder,
carper,
backbiter,
caviller,
reviler,
vilifier,
slanderer,
libeller,
calumniator,
defamer,
traducer,
mud-slinger,
knocker,
nitpicker,
asperser,