attentiveness has 3 distinct synonyms spread across 1 of its 3 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is inattentiveness.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
paying particular notice (as to children or helpless people)
“his attentiveness to her wishes”
the trait of being considerate and thoughtful of others
the trait of being observant and paying attention
Synonyms, antonyms and the broader and narrower relations for attentiveness come from Princeton University’s WordNet. Full sources and licences.