Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
exĭtĭālis, e, adj. [exitium], destructive, fatal, deadly (rare but class.): exitus exitiales habere, * Cic. Verr. 2, 5, 6, § 12: donum, Verg. A. 2, 31: scelus, id. ib. 6, 511: animalia venenata magis exitialia, si, etc., Plin. 10, 72, 93, § 198: criminosum et exitiale habebatur, Suet. Calig. 50.
Adv. exĭtĭālĭter, perniciously: amare, Aug. Conf. 6, 7.