Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
marvellous [ˈmɑːvləs] (US) marvelous adj восхити́тельный*восхити́телен , изуми́тельный*изуми́телен
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
Русский: