Olá,
Minha sugestão: to bad-mouth someone/something
bad-mouth someone or something: to say negative things about someone or something. Ex: Mr. Smith was always bad-mouthing Mrs. Smith. They just didn't get along. John bad-mouths his car constantly because it is too small for him. (dizer coisas negativas, falar mal)
Suas frases ficariam: Ele falou mal de você - He bad-mouthed you. Ela fala mal de todo mundo (She usually bad-mouths everyone) -*usually-geralmente: só para melhorar a frase

Aguardando outros termos...
Anne.