There's an adage that everyone is the hero of their own story, and I think the key to writing interesting villains is to embrace that idea.
Take Thorn of Dentonhill
for example. (Sorry, it's a book I know really well.) Willem Fenmere,
the crime boss of the Dentonhill neighborhood, is definitively the
villain. But at the same time, one could easily write the same events
as a book that's embedded in his sympathies. Here he is, a successful
underworld boss who's built an empire, and some mysterious upstart,
outside of the system, starts chipping away at it. At first it's just a
nuisance, but it quickly escalates. How and why is this happening to
him? Is it an old score being settled, or just the inevitable result of
being the old man at the top of the ladder?
I actually like writing my antagonist POVs, unless something in the story structure takes it off the table. (A Murder of Mages,
for example, wouldn't be much of a mystery if I just showed you the
killer's POV, right?) I think it goes back to my theatre and acting
background. Villains are the most fun, after all. Heck, some of my favorite scenes in Thorn are where Fenmere is dealing with the Blue Hand Circle.
best advice I can give for writing villain POV is to write them like
you want the villain to win. At least for that moment. Don't give them
stupid mistakes for the sake of propping up the hero. When you're in
there, writing that scene.... root for them. And that'll come through
in the writing.
Just a reminder, I'm at Boskone this weekend. Check out my schedule, and come say hi! I don't have a signing period scheduled, but I'll gladly sign any copy of Thorn shoved into my hand at any reasonable moment. Though I do stress: reasonable moment.