In a manner that deserves blame; culpably or in a way worthy of criticism.
From 'blamable' plus the adverb suffix '-ly.' This adverbial form describes how an action was performed in a blameworthy manner.
You can say someone acted 'blamably' versus 'innocently'—the adverb form lets you describe not just what someone did, but the moral character of how they did it!
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