So, we have a serious Gilgamesh here.
1. He will make use of Sha Nagba Imuru, immediately knowing everything about Mami, as well as every possibility. This will allow him to choose the optimal course of action. Right from the beginning, he has huge knowledge advantage.
2. SNI in combination with Ea is the argument we use the most, for a good reason. She cannot survive Ea, therefore it's a win button for him. What is important to mention is that Ea doesn't require some long preparation time. We've seen in Strange Fake that the very action of spinning Ea starts the act of devouring and cracking of reality, with Void spilling everywhere. It's also worth mentioning that he is holding Ea, while everything around him is devoured, which does mean that things like projectiles would be devoured as well. And Ea has no effect on him, even though some his other weapons are shown capable of harming him (such as the light from Merodach). Pulling Ea from GoB is easy and fast enough to the point it's not worth mentioning.
3. I imagine his mind manipulation resistance is strong enough to negate Mami's mind manipulation. He doesn't have an answer to reality warping, though. Reality warping is something Divine Spirits are capable of doing, and I don't remember him having anything to counter that, since it doesn't fall under normal magic he resists, if I remember correctly. I'm not sure what we consider as normal magic anymore, seeing as we started treating Time Stop as True Magic and not normal magic.
Overall, I think this is enough for him to win, depending on what Mami starts with. There is also Ship of Light for lolz.
