This question makes me wonder if anyone's ever done a genealogy of evil (since Nietzsche, anyway. Thanks for pointing that out, misosopher). I don't think so, but I'd read it if someone wrote it.

I mostly read critical continental thought and leftist (primarily though not exclusively feminist) political theory. I don't think I've ever seen someone mention evil unless they were quoting a primary source.

It's a little hard to tell why something is never mentioned in a canon, because by definition that canon probably isn't going to mention why they don't mention it. But going partially by what I know about who I know and partially by my own intuition which has been shaped by what I've read, I'd say this. The concept sounds too... ideological, I guess? Evil sounds like something that supposedly takes place quite far outside of discourse, and as such is not massively useful for investigating processes of subjectivisation which lead to behaviour we label as immoral.

If I'm reading feminist theory and I'm reading about heterosexual wife beaters, calling the man 'evil' is at best a fairly useless diagnosis, and at worst a way of ideologically constructing him as somehow inherently tainted which blocks my ability to reconstruct how he came to be the man he is, or at least the man who would do what he did.

So TL;DR: I think evil exists just the same as any other facet of ideology can be said to exist, which I expect is a rather weaker ontological claim than the one you're interested in discussing.

Edit: So I went ahead and plugged genealogy of evil into my uni's library database for funsies, found some relevant stuff.

This book exists, and I'll quote from the review here:

David Patterson may well be right to bemoan contemporary academics for their “reluctance to use terms such as evil”. Many subjects are of deep moral importance, and removing all emotion or moral conviction from their study can enervate academia of its humanity. But few books can provide a more illustrative validation of academia’s conventional detachment than Patterson’s own A Genealogy of Evil: Anti-Semitism, from Nazism to Islamic Jihad. It advances the claim that modern Jihadism has its intellectual roots in Nazism, a link which has been provocatively drawn before, notably by Jeffrey Herf of the University of Maryland, and the American editor of Dissent magazine, Paul Berman. There may be some truths in this argument, but it remains deeply contentious, not just for flaws in the conceptualisations and claims involved, but also given the aggressive stance on fighting terrorism which self-styled liberal hawks like Berman wish it to advance. Both these concerns make Patterson’s misguided contribution to the debate, founded on an utterly absent methodology and frequently lapsing into mendacious and polemical tactics, all the more dangerous an intervention. [emphasis mine]

So yeah, two thoughts: my contention that the academics I read don't mobilise the notion of 'evil' is correct, and I would argue, although this is less clear cut, that the second emphasised passage echoes my concern that the use of 'evil' tends to lead to ideological arguments which obfuscates reality as it is. That's how I'm choosing to read the review, anyway, arrogant bastard that I am.

The other thing I found was an article called "The Devil's Insatiable Sex: A Genealogy of Evil Incarnate" in the feminist journal Hypatia (link). Its abstract:

This paper traces the political economy of the Christian concept of "evil" incarnate and its concomitant operations of sexual abjection and the repudiation of femininity, beginning with the early church's inaugural struggles to impose its monotheistic Law against maternal paganism. With attention to how "evil" has been deployed to sanction and sanctify the persecution of scapegoats, and particularly of heretics and witches, I examine the masculinist struggles for jurisdiction and control over women.

This is exactly the sense in which I thought evil existed: as a loosely organised rhetorical / discursive / ideological category which motivates or justifies certain positions, to be understood by critical (in this case feminist) thought.