The most awful story in the world may well be the tale of Cain and Abel. In the Bible (Genesis 4), both Cain and his brother Abel offer sacrifices to God. Cain offers plants; Abel presents animals. "And the Lord had respect unto Abel and to his offering; but unto Cain and to his offering He had not respect."
Why? We are not told. But the answer is implicit in that silence: God can do what He likes; ours is not to question why. We must simply accept what God has ordained. Of course, commentators have sought to sanitise the tale not by explaining it, but by explaining it away. The most typical commentary is that Cain harboured unworthy thoughts even before his offering was rejected. But that is not in the text. The text offers us a God completely arbitrary in His whims; a God who does not acknowledge any moral standards for Himself. So, is it any wonder that "Cain was very wroth, and his countenance fell" - or that "Cain rose up against Abel his brother, and slew him"?
This is the God of the Bible: the God who later (Genesis 22) will test Abraham by ordering him to kill his son Isaac (or, in Muslim versions, his son Ishmael), and who spares Isaac/Ishmael only after Abraham shows his willingness to kill his son in God's name. That is perhaps the second most awful story in the world.
The reason the story of Cain and Abel is still worse is that it shows that even the kind of corpse-like obedience (Kadavergehorsam in German) which the God of the Old Testament demands from Abraham may not suffice to placate Him. Cain's sacrifice was at least as good as Abel's; better, indeed, if you don't like sacrificing animals. But Yahweh decided to show He was God by saying no to Cain and yes to Abel - thus indirectly causing Abel's death. Yahweh may make rules of morality for us - but need not obey them Himself. He not only has a giant's strength (which Shakespeare reminds us is excellent) but uses it like a giant (which Shakespeare reminds us is tyrannous). Yahweh's motto with respect to power is: If you've got it, flaunt it.
Those who continue to believe in God may, should they meet Him after they die, be in for a nasty shock if He chooses to flaunt his power by damning them anyway - just to show He can. In such circumstances, it is perhaps imprudent to take too seriously the national motto of the United States, which appears on that country's banknotes: In God We Trust. We might do better to trust our own conscience and hope for the best - but take nothing for granted.