Nouns

(n)denigration, belittlinga belittling comment
(n)belittlingthe act of belittling

Adjectives

(s)belittling, deprecating, deprecative, deprecatory, depreciative, depreciatory, slightingtending to diminish or disparage“belittling comments”, “managed a deprecating smile at the compliment”, “deprecatory remarks about the book”, “a slighting remark”