The Protective Dome
With Reign now having conquered the city together with his men, he was able to easily integrate it into his territory with a portal. His allies had also joined in the battle after Beast had explained how large the city was and how powerful of an enemy they had faced, but the battle they were expecting to happen never occurred in the end.
Thanks to Reign and the others using Jack and the other three personal guards of the Butcher, they were able to kill the enemy Tier IV combatants bit by bit and decrease their strength by a considerable amount before the final battle took place.
With most of the Tier IV combatants being eliminated, the enemies that were left were simply far too weak to truly pose a challenge, which led to their quick and easy defeat, culminating in an anti-climactic final battle.