What is 'evil', and does it exist objectively? The metaphysics of good and evil. Glad to chat with you again Jack, glad you've been well. To me, good is what we "ought" to do, and evil is what we "ought not to do". In other words, "This should exist, and this should not." But why do we think certain things should exist while others do not? Taking it from a purely human standpoint, we would come up with a myriad of opinion. That won't do. We need something more concrete. Something more primitive.
Why should humans exist at all? Which then I can say, why should life exist at all? Which leads to, why should anything exist at all? And there is our final question, the base upon which we can build our logic. An interesting fact, is that much of the "substance" that resulted form the big bang is gone now. After billions of years, its cancelled out or gone the way of entropy. But not the matter that's stuck around. That stuff, which we're made of, has stubbornly refused to go into the dark. That matter, is what life is built off of. That matter, is what we are built off of. And that existence, is what ethics is built off of.
The matter around us continually seeks to remain as it is. Forces jostle around, elections shift and molecules combine and break apart, but the underlying matter and energy remain. Life is a combination of matter that continues to seek its own continuation, even in the face of outside forces. Thus the prime directive is, "Should I continue to exist?" Life does with rudimentary intelligence. Humans come along and can see how it is. They can decide. Should I continue to exist? Most of us choose yes. That is good. Existence is good.
You also might realize that existence extends outside of yourself. And there is existence within interacting with yourself, and other existences. A fly alone and a human alone are two existences, but when they come together, they create a third interaction of existence that could not be otherwise. You see it in the atoms that form into different molecules. The interactions of so many different expressions of that existence. This is good as well.
At that point you might realize that if one can preserve one's own existence, and promote other existences where you can, then that would create more existence, and thus more good. Sometimes there must be destruction, or a change in the makeup of matter to preserve some existences over others. Life must continue to obtain energy to live, which means something else must lose it in return. What must exist and what must be destroyed are the constant calculus of morality.
I have a feeling no one person can answer that calculus. I have a feeling there is no one theory that will apply to one situation, but to many situations. The one thing that I feel confident in, is the underlying goal and result of all of those theories should be to preserve and/or create as much existence as possible.