"What qualities make a god good or evil?"
The question assumes the first horn of the Euthyphro, that good and evil are things other than god and determines whether a god is good or not. All of us have the intuition that there is good and evil, and that good refers to a standard we should uphold, and evil refers to the avoidance of that standard. We have three choices in which to ground that paradigm, we can ground it in something outside god, we can ground it in a gods commands, or in the case of Christianity we can ground it in God's nature. In the case of the Christian God, God's nature doesn't make something good, good simply refers to God's nature. Good means like Yahweh, and Evil means not like Yahweh. One might say, "But why is it that what is Good is Yahweh's nature, I have this intuition that tells me there is objective Good, so why should I attribute it to Yahweh?" Well that is to go backwards, to the first horn, by thinking that Good is some standalone referent or entity that stands as a paradigm for sorting goodness from evil, well that standalone entity or referent is God's nature. When you love Good, you Love God's nature. When you love Evil you hate God's nature. And each of us have love and hate for God's nature in us. We are quick to love the parts of God's nature that do well for us, and even quicker to hate the parts of God's nature that stand against our desires and ambitions.