The invention relates to a torsional damper for a torque-transmission device, which comprises: a first element (1) and a second element (2) which are rotatable relative to one another; and a first damping means and a second damping means, each damping means comprising a resiliently deformable blade (9) comprising an attachment portion (12) and a resilient portion (13), a bearing element supported by the other one of said first and second elements and arranged, for an angular displacement between the first and second elements relative to an inoperative angular position, such as to exert a bending force on the blade, said damper being characterised in that the circumference of the resilient portion of the blade of the first damping means increases beyond the attachment portion of the blade of the second damping means.