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

[Neo-Scholastic]

What the fine tuning argument is saying; is that the evidence shows that something capable of choice and direction is responsible for what is being seen.  It also makes the notion that there is no purpose or intention behind what we see as difficult.

I would refer you to Thomas Nagel's "Mind & Cosmos" who similarly argues that excluding purpose and intention from nature, by fiat, is to deny the obvious - teleology is an essential feature of the world. Ultimately, Nagel rejects theism, but goes so far as to admit his bias - he, like any of a multitude of skeptics here, doesn't want theism to be true. The way I see it, Nagel, is on a dead end quest to recover Aristotelian Final Cause with out any theistic entailment.