A heavy-duty shredder, in particular for use in forestry, has a frame; a rotor, which is mounted on the frame so that it can rotate about an axis of rotation and has a drum coaxial with the axis of rotation; a plurality of annular discoidal sectors extending around the drum, integral with the drum and distributed along the axis of rotation so as to form annular cavities between the adjacent annular discoidal sectors; a plurality of first teeth integral with the drum and arranged in the annular cavities between two adjacent annular discoidal sectors; and a plurality of second teeth integral with the drum and aligned with the annular discoidal sectors.