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

[SteveII]

If you think there is not 100% established mind-boggling low probability, then you do not understand the issues. Physicists and cosmologists agree that the universe is finely tuned. Martin Rees, who wrote the list above (from the wikipedia article), has impeccable credentials: https://en.wikipedia.org/wiki/Martin_Rees

In fact it is so well established that the multiverse theory was dreamed up to account for it!!

https://www.youtube.com/watch?v=R97IHcuyWI0

Sean Carroll seems to disagree completely. However, for the sake of argument, let's grant that the universe is indeed finely tuned. Even if this is the case, we're not one step closer to demonstrating that any deity exists. All we've done is show that the universe was fine-tuned by something. That something could be a million different things. What makes you think a god is a more likely fine-tuner?

You mean there are other alternatives to consider? What? 

If you are going to say the Multiverse, then you have just pushed back the problem. If order for any multiverse to spawn billions upon billions of universes--each unique in its physical laws and constants, doesn't it too have to be fine-tuned to do so?