Complex sentence: Just as Windu is about to overpower Sidious, he unleashes Force lightning at Windu but deflects it back with his lightsaber at Sidious, deforming his face into the wizened, yellow-eyed visage seen in the original films.
Split into simpler sentences: Just as Windu is about to overpower Sidious, he unleashes Force lightning at Windu. Windu deflects it back with his lightsaber at Sidious, deforming his face into the wizened, yellow-eyed visage seen in the original films.