diminish

(verb) decrease in size, extent, or range. Synonyms: decrease, lessen, fall. Examples: "The amount of homework decreased towards the end of the semester." "The cabin pressure fell dramatically." "Her weight fell to under a hundred pounds." "His voice fell to a whisper."

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