In a manner that causes suffering, pain, or distress; in a way that troubles or burdens.
From afflicting plus the adverb suffix -ly, which transforms adjectives into adverbs describing how an action is performed. Common in formal or literary English.
Adding -ly to an adjective is so intuitive that children learning English naturally create adverbs this way, even for made-up adjectives—showing how deeply this pattern lives in our language brain.
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