belittle

(verb) cause to seem less serious; play down. Synonyms: minimize, denigrate, derogate. Example: "Don't belittle his influence."

(verb) express a negative opinion of. Synonyms: disparage, pick at. Example: "She disparaged her student's efforts."

(verb) lessen the authority, dignity, or reputation of. Synonyms: diminish. Example: "Don't belittle your colleagues."