As someone else has pointed out, I understand that psychopathy is a scale rather than a "yes/no" and I don't actually have much of a problem with functioning high-end-of-the-scale people in many instances.
As an example, I would rather be operated on by someone with little to no empathy for me who was meticulous and unstressed by their work than someone whose concern and empathy could distract them or cause them to suffer afterwards if something went wrong.
I also have never understood feeling actual sadness at the death of someone you don't know (the Princess Diana thing baffled me) but can't bear to watch films in which children are mistreated in the slightest way so sometimes I think it's just a case of people having different triggers.
That said, I do believe I know one 'malignant' person who'd probably score highly if he was actually honest about the checklist (unlikely). He's an acquaintance I see occasionally by virtue of common friends with dead, predatory eyes and he gives me the chills. I've spent enough time with him to truly believe he has next to no sense that other people have an internal life that is in any way important. He plays with them in a very detached way.
He happens to be intelligent with a decent job and connections. His charm, though it clearly works for him in many cases, is a bit 'off' and a lot of women I've spoken to over the years have their alarm set off around him whereas the vast majority of men seem not to. He's quite entertaining (from a distance), to be fair about it.
He's well aware that I don't like him and has prodded me on the subject a number of times. I was quite blunt with him on one occasion and he now generally leaves me alone. As it is, I think he thinks my opinion can be safely ignored so long as it doesn't seem to be having consequences for him, and I only discuss my opinion with very close friends. So, truce, I suppose. I would be very far from shocked if he had committed hideous crimes if there served his purpose or simply if he thought he could get away with it.