disparage, belittle, pick at - express a negative opinion of; "She disparaged her student's efforts"

talk down - belittle through talk

accuse, charge - blame for, make a claim of wrongdoing or misbehavior against; "he charged me director with indifference"

assassinate - destroy or damage seriously, as of someone's reputation; "He assassinated his enemy's character"

libel - print slanderous statements against; "The newspaper was accused of libeling him"

badmouth, drag through the mud, malign, traduce - speak unfavorably about; "She badmouthes her husband everywhere"