What percentage of the gravitational binding energy released during collapse is carried away by neutrinos?

Roughly 99%.

The core collapse releases an immense amount of energy stored as gravitational potential energy. While some of this energy manifests as the kinetic energy of the infall and the thermal heating that drives the initial shock, the vast majority is carried away by a flood of subatomic particles known as neutrinos. These particles are generated in enormous quantities during the core's extreme compression. Neutrinos interact very weakly with normal matter, allowing them to stream rapidly out of the dense stellar interior. This neutrino emission accounts for approximately 99% of the total gravitational binding energy liberated by the collapse. This overwhelming energy loss through neutrinos is crucial because it is the subsequent re-deposition of a fraction of this energy back into the stalled shock wave that provides the necessary thrust to drive the visible supernova explosion.