Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
peremptory [pəˈrɛmptərɪ] adj (pej)(person) вла́стный*вла́стен , категори́чный*категори́чен (:order, instruction) категори́ческий#
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.