Continue climbing until you reach the bridge. Head left until you reach a building. Open the door and watch the scene. After the scene, you'll be taken outside. Take out the enemies and the massive, infected head of Aegaeon will start chewing the platform. You have fend off the group of enemies around you while making sure you hit the red fangs on the side of the platform. Keep attacking and prioritizing the red fangs until you get thrown off to the next ledge.
Once there, you have to fight and weaken the infected hand. It will only have attack; it will use its claws to smash the ground three times. These are easily evaded. After the third attack lands, quickly head to the right and attack the infected hand. This will also allow you to evade the fangs on the left. Keep attacking until you can grapple it. Once you're able to grapple it, press any of the attack buttons to control the infected hand and deal damage to Aegaeon's face.
Once damage has been dealt, Kratos will grapple Megaera. Press the attack buttons to finish her off and to complete the chapter.