In general, the fixed side of BBs can be hard. Do make sure that you are twisting in the right direction! That said, wrenches that fit the BB cone don't always give one the leverage needed. To get that, one can put the flats of the cone in a vise, and use the bike to as a wrench. But it depends upon the design. Old school campy cones have flats. New stuff ... I don't know.