Morality is itself a direct product of both empathy and agency, though. Seriously, you can essentially reduce it to those two factors alone. If you remove both then they're no more evil than a natural disaster. They may still have agency, but empathy would be the factor that informs moral agency.
I think the entire reason they're 'evil' is because you're taking an ego and separating it from any moral framework. An ego placed in such a situation without the controlling influences will incline towards what we see as 'evil'. It's a paradox, but they can be external to any moral framework (in terms of intent, perspective, etc) and still for all of our purposes be 'evil'.
Well, that why I said that he could be an evil tool. He is different from a natural disaster, however. No one
made hurricanes, they just happen from natural circumstances. Femto was specifically crafted by the Idea of Evil to do a specific thing: Cause as much harm as he can. Hurricanes have no will and aren't controlled by anyone. Griffith has his own will while also made for a evil purposes.
Second, there are things such as moral sociopaths. Or, at least, ethical ones. Their lack of empathy means they can't truly care about people around them in terms of feelings, like most normal people do, but they can still follow certain rules because they know, on an intellectual level, that it is wrong, by adhering to some ethical system (usually utilitarianism, iirc). Griffith is still capable of this as femto, because even if he doesn't feel what he felt before, he still knows that what he did to them and the rest of the Band of the Falcon is wrong. When he was griffith, he tried to ignore that for his dreams, but as Femto, he truly doesn't care. But that does not mean his understanding of morality has disappeared. That would be like losing your understanding of what colors are just because you've been blinded. In this way, Femto is still culpable for his actions in a regular human way. Complete sociopaths from birth are capable of developing ethics. Griffith was an adult before he was turned. He knows right from wrong and chooses to do wrong for his own purposes. That's not much different from many regular humans.