A person who criticizes or blames someone; one who expresses disapproval.
From discommend (to criticize) + -er (agent suffix creating a noun for 'one who does'). This follows the English pattern of turning verbs into nouns describing the person performing the action.
It's fascinating that we have specific words for people who criticize—'discommender' sounds like a medieval title, like you've been officially appointed to find fault with everything. It's almost respectfully mean.
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