When people use the word "god" it's meaning is often implicitly assumed, rarely identified, almost never defined in a testable way. How do you recognize a deit

When people use the word "god" it's meaning is often implicitly assumed, rarely identified, almost never defined in a testable way. How do you recognize a deity? Which observable, ideally measurable, features should one be looking for? The concept of god used to be simple: Anything more powerful then me is a god. A very simple test and the existence of gods is obvious. Then we started to add more and more and also expect more and more from our gods. Currently we seem to expect them to be omnipotent, omnipresent, omni-whatever… which is really pushing it beyond even internal consistency, let alone observable reality. I wonder what would (in the 21ste century) be considered evidence of a "god"? Would we classify an actual existing Zeus as "god" or just as a member of a more powerful intelligent species? Would we apply the term "god" to the god of the Hebrews? Or would we rather consider it to be a very advanced alien? Imagine this speculative scenario: Next week a very powerful non-human entity will manifest itself on earth. It will claim that it is the representative of the creator of the universe and that has seen how the creator made life on earth. What could it present as evidence which would convince you that what it was saying is actually true? What evidence would convince you that it's not just a delusional alien with more scientific and technological knowledge and very advanced technology?