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

[Mister Agenda]

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.

1. No assumption. It's impossible for a universe not to have law and structure unless it was designed that way. A completely lawless (a universe with no regular features at all) universe would require intelligent design, the only way to completely eliminate regular features from chaos...because complete lack of regularity is itself a regularity. Your 'billionth of a second' universe has characteristics, and that's what physical laws are.

2. I didn't bring up multiple universes, but again, you lack the intellectual integrity to stop pretending you don't know that the multiverse wasn't posited to explain the universe but is a consequence of the physics involved in explaining what we can observe of the origin of the universe. No one made up multiple universes as an ass-pull to prop up a refutation of the FTA. And someone who posits their favorite deity as an explanation for a scientific mystery and smarms about Occam's Razor ought to burst from the hypocrisy.