I think you are right. Some examples: That's the wrong man - Αυτός είναι ο λάθος άντρας. They caught the wrong man. - Έπιασαν τον λάθος άντρα.
Λανθασμένος, -η, -ο would be first of all something that has a mistake or mistakes, that is erroneous (and therefore is wrong), e.g. μια λανθασμένη απάντηση. That would also be my first translation for ο λανθασμένος άντρας: 'the erroneous man' (which makes no sense). As a next step it could be used for an action that is faulty in some respect--e.g. ethically--and therefore wrong, e.g. ένας λανθασμένος πόλεμος - 'a wrong war'.