An all-powerful being who created the universe.

Thanks. That's a nice, succinct description.

Interpreting/expanding what you wrote, I think you're saying that God is:

* something that currently lives, or maybe lived in the past ("being"),

* that is not limited in any way ("all-powerful"),

* that created, from nothing, everything other than themself that has ever existed and that will exist in the future ("the universe")

Is that close?

Yep. Although for the first point I don't think "live" is the right word because God's existence is very different from a human existence. And to expand on that, God has always existed and always will exist.