The quality of being excessively sweet, pleasant, or satisfying in a way that becomes tiresome or disgusting.
From 'cloying' (adjective/present participle of cloy) plus '-ness,' creating an abstract noun for the quality or state of being cloying.
The cloyingness of overly sentimental movies explains why some people find them unwatchable—there's a psychological limit to how much emotional sweetness we can stomach before our brains reject it as fake.
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