>I think that taking unironic pleasure at the misfortune of others, or wishing others harm, and the capacity to do so, is the literal opposite of empathy.

Wishing others harm and being able to empathize are tangential concepts.

The ability to understand what it's like to have something terrible happen to you does not preclude you from wishing it upon your enemies.

I suspect that for a subset of people the ability to empathize with people who are suffering makes the suffering of their enemies all the better.