Honestly, for me the easiest thing that knocks down the notion of a singular god is the fact that damn near every culture for human history has had some form of religious belief, and all of them have been convinced that their belief is the correct one and everyone else is wrong. The idea that somehow we've always been getting it wrong but now SUDDENLY, the bible's got the ultimate truth and is the right one, is ridiculous to me.
I don't begrudge anyone their faith (and in fact really appreciate and like having multiple perspectives here in the FIYH community), but for me personally, it's infinitely more likely that everyone is wrong, than any one particular sect being right and everyone else being wrong.
Whether an all powerful creation-entity of some form exists is an open question that is simply not answerable, since if it doesn't there'd be no evidence of that, and if it does, we are so micro-scale by comparison that we'd have no realistic way of measuring it, at least not until we start exploring the boundaries of the universe.
I'm damn certain though that none of the specific theologies that have developed over the course of human history are accurate, and none of the more modern texts are any more plausible than the roman or greek mythologies of old, they're just as ridiculous and outdated.
The more we learn about the universe the more it is apparent that humanity is an infinitely tiny piece of the larger puzzle, and if there is any creator running the show, they operate at such a larger scale that they certainly don't give a shit about humanity's "sins", or any other human-specific emotional construct that we've happened to develop as a civilization over our measly couple thousand years of existence.