Before we can discuss what there is that needs to be explained about evil, we must first have a working definition of evil: we perceive something as being tainted by evil if it by its nature results in consciously experienced suffering, whether as a result of physical pain, emotional pain, purposelessness, disorder, untruth or ugliness.
There is nothing to be explained about evil, unless we assume that God exists and is totally good. For if there is no God, or God is beyond good and evil, then 'evil' is merely a word that we have invented to categorise things that we don't like, a word that does not resonate because it can't be defined constructively. We can fill libraries with books on the subject of evil and yet reach no conclusion, because the concept is unsound.
Let us therefore proceed on the assumption that God does exist and is totally good. In that case, we must provide an explanation as to how evil could arise in a manner that does not make God to be its author. Note that this cannot be explained away by maintaining that all evil is ultimately just misunderstood good, for then we are effectively saying that God is evil as well as good. Its one thing to say that all the evil that overcomes us will be turned to our good, and another entirely to say that this means that evil isn't really evil. Evil is really evil, and if God is in any way responsible for it, then He is not totally good, period.
The mainstream Christian explanation is to say that we don't have an explanation, but hope that there is one. Such an explanation would have to have at least one explanatory element, resulting in an Occam score of at least 1000.
Another approach is to say that God is essentially, rather than totally good. He may create evil in order to achieve a higher good. This explanation has the disadvantage of being contrary to the Bible, for example in the statement that God is light and that in Him there is no darkness at all. It also leaves us with the necessity of explaining how all the evil we see around us will be turned to good. Again, the mainstream Christian response is to say that we don't have an explanation, but hope there is one. Because evil is a many-headed monster, such an explanation would have to be at least complex, resulting in an Occam score of at least 3000, making us worse off rather than the better for denying the total goodness of God.
QO offers another explanation, one which enables us to maintain both that the One is totally good and that evil is fundamentally real. We call this explanation the Turing Twist. It has an Occam score of 0000, relative to QO.