If someone lacks empathy, do you think that makes them evil?

No.

not clear thought, could be.

This article might interest you.
https://www.quora.com/What-do-people-who-lack-empathy-act-like

There are definitely degrees to empathy and how extreme you take it. But mostly important when it comes to human interaction. Lacking empathy for people has its degrees but lacking it, would fefinately make you evil. If you cant identify with another persons position when you do or say things to them it opens the door to people not liking you.

A lot of serial killers and those who commit school shooting generally lack empathy for human life so it's easy for them to justify causing harm to others in their minds.

A lot of brutal people lack empathy but since you ask I would have to assume you at least have some empathy or you wouldnt even bother asking, you simplely wouldnt care.

http://www.kennethrobersonphd.com/aspergers-syndrome-problem-empathy/

Dropping the "evil" word altogether lacking empathy in some social demographics may be a sign of the "human ecosystem" requiring some percentage of the population to be able to perform a number of undesirable NECESSARY tasks that otherwise would be left unfulfilled. That said people without empathy can be dangerous, psychopaths being the most common example. The better question for Anthropologists and Sociologists would be to ask why do a given percentage of the population, a very stable percentage should I remind you, persists over the aeons without going extinct by natural selection ? To me it looks like the counter intuitive answer points to a NECESSITY in the ecosystem itself the likes we don't talk much about for lack of deep thought on the human complex ecology at work. The human sciences are highly constrained for political correct thinking that counteracts any progress in understanding these phenomena properly...

You may be mistaking 'lack of empathy' for either not understanding where someone is coming from or having no sympathy for it if you do.

I never met an 'aspie' who didn't have empathy. Usually they have an excess of it. Others just can't see it. But Don't lose sight of your own .

My take is that to be evil you have to do things WILLINGLY that you KNOW
are wrong.

Lack of empathy may make it harder for some people to perceive certain
things as wrong. That doesn't mean they are evil; they're just wired
differently.

Willingly entails "free will" right ? Well I don't do free will talking hence why the wording "evil" is nonsensical...One should rather talk about competence or lack of it, and furthermore in specialization regarding certain percentages of genotypes in the human ecology spectrum. Psychopaths are pretty stable at 3% and one should wonder why not 5% or why not 0.1%...if you are not curious about certain magic number in the human spectrum then you are getting the wrong approach to the all problem at hand.

Okay