Complex sentence: Just as Windu is about to overpower Sidious, he unleashes Force lightning at Windu but the Jedi Master 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.