depreciator

Synonyms:

detractor, disparager, knocker

Types:

backbiter, defamer, libeler, maligner, slanderer, traducer, vilifier

one who attacks the reputation of another by slander or libel

hatemonger

one who arouses hatred for others

muckraker, mudslinger

one who spreads real or alleged scandal about another (usually for political advantage)

Type of:

cynic, faultfinder

someone who is critical of the motives of others