Theists: What is the most compelling argument you have heard for Atheism?

[Brian37]

How could a multiverse create a universe without laws and structure? [1]

How would a near-infinite number of universes not address the issue of one having the values our has by chance? If you're literally asking why we're in the one that allows us to exist, you need to take a break. [2]

It's theoretical physics, which would more properly be named 'hypothetical physics'. It has to fit what we already know and the math has to work, but it ain't necessarily so. It uses the scientific toolbox, and (hypothetically) the hypotheses generated may be possible to test someday. [3]

1. It seems that you assume in your question that the multiverse is fine-tuned to spit out universes with laws and structure? On the other hand, since this isn't science anymore, why can't a universe be spawned that is just chaos and exists for a billionth of a second? 
2. So, Occam's Razor is out the window--on a grand scale. You are positing a near-infinite number of universes to explain this one. Not very parsimonious. Also, the multiverse is a metaphysical theory and will never be anything else--so any argument that has the multiverse as a component will always have that little asterisk next to it and never be, by itself, a defeater for a premise.
3. All true.

Waaa waaaa waaaa waaaa science.......waaa waaa waaa Allah. What, that doesn't work for you? 

Waaaa waaa waaa waaa waaa science........waaa waaaa waaa Yahweh. What, that doesn't work for you?

Waaa waaa waaa waaa waaa science........waaaa waaa waaa Buddha. What, that doesn't work for you?

Waaa waaa waaa waaa waaa science.....waaa waaa waaa waa Brahama. What, that doesn't work for you?

Listen Charlie Brown's "teacher", I know you really think you are onto something, but you are not. Wake up, grow up. It wont kill you to give up on old mythology.