jackass , jerk , cruel , dickhead , unkind , harsh , wicked , hateful , heartless , vicious , virulent , unrelenting , tyrannical , malevolent , atrocious , bastard , barbarous , bitter , brutal , callous , degenerate , brutish , depraved , evil , fierce , hard , implacable , rancorous , pernicious , inhumane , monstrous , merciless , inexorable .