tempered has 3 distinct synonyms spread across 1 of its 2 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 untempered.
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.
made hard or flexible or resilient especially by heat treatment
“a sword of tempered steel”
adjusted or attuned by adding a counterbalancing element
“criticism tempered with kindly sympathy”
Synonyms, antonyms and the broader and narrower relations for tempered come from Princeton University’s WordNet. Full sources and licences.