The strikes of thor. The great strikes of the Black Blood. Even as a heroic spirit, these strikes would most definitely have killed him. It would probably have even brought Berserker, the Greek legend with twelve lives who could only be harmed with a strike above a strength capable of destroying mountains to his knees.
However, this mongrel had not counted on one thing: He was the King, and she was but a mongrel.
Gilgamesh weathered through her attacks. He did not block. The King did not need to block. The King had also considered unleashing Enkidu, his most prized and treasured weapon to simply hold down the mongrel in place, but such a creature was unworthy of being bound by the weapon that bore the name of his best friend. Instead, he had stood through her attacks unharmed. How? One might ask?
Despite his arrogance, Gilgamesh was no fool. He had his own defence, just in the unlikely possibility that a few worthy ones had broken through his barrage. The King of Heroes, Iskander, and his beloved King of Knights Arturia were two such beings. And it was through them that the King had learned a small amount of respect. It was also through Arturia that he had discovered the means of his defence in his treasury.
Avalon. The Sheath of King Arthur; the ultimate defence, created by the fairies to hold Excalibur.
As Mia began her assault, as she taunted him, speaking blasphemy about her taking his weapons, Gilgamesh drew the sheath from the Gate of Babylon and implanted it inside of him. As a result, he was protected by the "ultimate defence". The sheath of Avalon defended Gilgamesh, protecting him by shielding him in an unreachable Utopia; the land of fairies which King Arturia herself was said to have gone after her death. It did not resort to crude simple "blocking" and "deflecting"; instead it isolated the user in a reality complete of their own. For all intents and purposes, it had elevated Gilgamesh to another plane of existence, one superior to the one in which the location he was standing in was struck by the blows.
"Is that all you have, Mongrel? Nothing but power, power and more power? Nothing but a means to remove power from others and add power to yourself?" Gilgamesh sneered as he revealed himself to be unharmed even as the very ground around him was destroyed with enough force to kill him twenty times over. "Such a basic, primitive concept. Such a brute will have no means of matching me.
Know your place."
And with that, the King of Heroes began his original assault once again, throwing countless legendary weapons at Mia, already tiring of the mongrel. He was not even truly seeking to punish her anymore; no, she was but a distraction. His true goal here was to face the great presence he had felt; but instead he had come face to face with this mad dog who reminded him so of berserker. And he had been infuriating enough.