Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
mĭsĕrātor, ōris, m. [miseror], one who pities, a commiserator (post-class.), Tert. adv. Marc. 5, 11; Juvenc. 2, 295; Vulg. Psa. 85, 15.