Omniscience is impossible. Omnipotence is impossible. The two concepts are so full of paradoxes as to be laughable. School children can and do tear them apart. Trying to combine both characteristics in a single entity results in a death spiral of ridiculous scenarios and infinite regressions. Attempts to add in other attributes such as personality (benevolence, justice, morality, etc) are non-starters, it just doesn't work.
Apologists have, over the centuries, whittled away at their definitions of omnipotence and omniscience in futile attempts to make them play nicely with logic. It is to the point that neither omniscience nor omnipotence are out of reach of the human race in a few hundred years of scientific advancement.
The only way "God" could exist would be if there were nothing special about him. In which case, why call him god?
Anyway, if anything came along claiming to be god, it would be lying, likely with intent to manipulate stupid people. I would probably try to kill it, too.
Also, saging a superstition thread on a science board. Take it to /x/, faggot.