hard-liner(A person who takes a firm position on some policy) noun [UK: ˈhɑːd.ˌlaɪ.nə] [US: ˈhɑːd.ˌlaɪ.nə]
integralistanoun {m} {f}
fundamentalist [fundamentalists](one who reduces religion to strict interpretation of core or original texts) noun [UK: ˌfʌn.də.ˈmen.tə.lɪst] [US: ˌfʌn.də.ˈmen.tə.ləst]