disparage
Definitions
To speak of someone or something in a derogatory or belittling way.
To lower in reputation or esteem; to discredit.
Examples
It is unprofessional to disparage your colleagues' work during a team meeting.
The critic did not hesitate to disparage the film, calling it a complete waste of time.
She refused to disparage her former employer, even though she had many reasons to be upset.