But the “formal” response is that this person could talk, digest, enjoy simple pleasures, think, and generally show many of the simple skills and “goods” of being a human person.
He may have had a deeply corrupted will and utterly foul notions of what others owed him and he owed them. It may have been unlikely to the point of unimaginable that he could or ever would understand the evil he had done and embraced — much less turn from it. But, as you might say, he did that evil with “goods,” goods like intelligence, focus, physical strength, and the faculty of choice.
All of these goods were horribly distorted, tainted, fouled by his misuse of them. But that they were there to be misused was, in itself, good.
However despicable and contemptible a sinner may become, there is, I think, an inescapable tragic aspect to sin because to the destruction of wonderful capacities.
There used to be a popular poster, in which a kid said “I know I must be something good, because God doesn’t make junk” (or something similar). It gets you thinking - if God made a murderous skinhead, there must be SOMETHING good in him, or else God would have never created him.
However, the older I get, and the more stories I read about where people are brutally murdered, the harder it is to believe that there aren’t people in this world who are nothing but evil. Maybe they aren’t created evil, maybe there is a shred of decency left in the corrupted soul...but its hard to see.