brainwashed has no recorded synonym. 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 unbrainwashed.
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.
subjected to intensive forced indoctrination resulting in the rejection of old beliefs and acceptance of new ones
“brainwashed prisoners of war”
Synonyms, antonyms and the broader and narrower relations for brainwashed come from Princeton University’s WordNet. Full sources and licences.