Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
damnātor, ōris, m. [damno], one who condemns (late Lat.), Tert. ad Nat. 1, 3; id. adv. Marc. 1, 7: damnator Christi frater iniquus, Sedul. Hymn. 1, 10 al.