There are 3 pieces of evidence I can think of that we should expect to find but that we fail to find:
First, we should expect to find at least one example of a prophecy being foretold either in the bible or in another holy book which clearly comes true. Christians have claimed that such prophecies exist, but upon investigation none of these alleged prophecies are specific enough to convince an intelligent person that these were the result of divine foresight. They are far too ambiguous to be convincing.
Second, we would expect to find some examples of divine miracles. That is, we should expect to be able observe some instance of a phenomenon in which the religious explanation is more plausible than the scientific one. We do a see a number of unexplained occurrences in nature for which there is not yet a known explanation, but never have we observed a miracle take place before our own eyes. For all that science has been able to study in full, we have found naturalistic explanations in every case.
A final piece of evidence I think we should expect to find is the revelation of new information from those who claim to have had experiences of divine revelation. If people truly were in contact with a supernatural being beyond themselves, why is it that they can never tell us anything about reality that we don't already know? Even people who claim to have died who describe having a transcendent experience always come back with the same generic story which lines up with what's written in their holy book. That suggests to me that these experiences are not supernatural but are best explained as projections of the human imagination.
Upon failing to find any of the evidence we should expect to find, I think it's therefore more reasonable to believe that God does not exist.