This is just my opinion, but I think you’re employing two fallacies here.
#1, you’re not just talking about a capacity for doing evil, but actually doing evil. Everyone has the capacity for doing evil. Everyone is evil. This is both Biblically and experientially true. So it can’t be capacity for evil you’re talking about, but actually doing evil. You can call it whatever you want, being weaker, or being more sensitive to temptation, whatever, but in the end the only real criteria you can have is that someone actually does more evil. They have more capacity for evil because they have actually done more evil.
Any other criteria of “capacity for evil” is unmeasurable. In my view. How do you know that someone is tempted more than someone else? Or that they’re weaker than someone else? There’s no way to tell unless they actually do more evil. It might be that someone who seems super good internally actually goes through incredible struggle with temptation. But you can’t *really* know that. Anyway.
And that seems contradictory. That you must actually do evil to be more good. On a purely secular logical standpoint, seems odd.
Which gets to #2 – there’s an assumption that being empathic is tantamount to being good. That is, that empathy is the only thing (or at least the most important thing) about being good. I don’t think that’s necessarily true. Why should empathy be the most important part of being good? I don’t think it is. Maybe that’s just me.
So for myself, I do not believe that you can meaningfully talk about relative capacities for evil unless the criteria involves how much evil people actually do. And I cannot believe that you must do evil to be good. Nor do I believe that empathy is the only or even the most important part of being good, even in a relational sense. But that’s just my opinion.