I understand why romantic suspense and thrillers need a bad guy, but I prefer the idea of one to the reality. And for less scary romances, I can do without a specific third party as an antagonist.
As a reader, I skip all sections written from the villain's POV. (I love when those sections are in italics so it's even easier to see when they end.) I've got my reasons.
Of course on paper, the psychopathic pedophile poet can reveal the psychopathy but not the poetry lest we figure out whodunnit. But what's fun about being in a psychopath's head? So the POV scenes are hokey and unbelievable. Why read them?
Second, it's a bad way to build suspense. Bad guys are planning bad things. We get that part. In a movie, you frequently get a camera angle that suggests there's a baddie lurking in the shadows -- that builds a lot of tension. But books work differently. Better (I think) to stay in the protagonist's POV in a scary situation. We like that person, we're concerned for that person, we may even identify with that person. If they're looking at shadows, hearing strange noises, driving on a deserted road -- we're right there, scared for (and possibly with) them.
Okay, that's suspense/thriller/dark paranormal territory, where the baddies break the law. What about more domestic romances? Even there, I'm not fond of antagonists. But before I go there, allow me to give credit where credit is due:
The best antagonist ever in a romance novel? I'd give that award to an unnamed person in Mary Balogh's Slightly Dangerous. If you've read the book, you know who I'm talking about. If you haven't read the book, read it -- if only to see how cleverly it's done.
Better would be the well-intended, even lovable, close friend, family member, or confident whose love and concern for one of the protagonists endears the antagonist to us even as he/she is working hard to prevent the happy ending we're waiting for.
The trouble with that scenario is that the protagonists themselves have a lot to do with such a situation. If Mom/Sis/Uncle Harry is interfering in the heroine's love life, who's given them permission to do that? The heroine, presumably. Well, that's pretty dumb on her part. Wake up and smell the toast, babe. Which is precisely what she may need to do in the course of her character arc: grow a pair, get out from her family's shadow, find her own feet, etc.
All good goals, but not entirely consistent with a romantic happy ending. I prefer my romantic protagonists to have done that work already, lest the romance be more about getting away from the family and less about the beloved. Yes, family members can and will meddle, but protagonists should have established boundaries that prevent the relatives from being true antagonists.
That leaves the jealous ex, the "other woman," or the plain old troublemaker. This is right up there with the Misunderstanding for stupid conflicts. Unless it's "Sleeping With the Enemy" territory (in which case we're back to thrillers), I have to wonder what a protagonist is doing listening to venomous tripe about the beloved? Tell the rat bastard (or evil crone) to crawl back into their lair and leave the romance alone.
My bottom line is this: in romances, as in real life, I believe that people do a far better job getting in their own way than what others can do for them. So I'm not a big fan of the external antagonist. I don't see any reason why the hero can't be both the goal and the antagonist for the heroine, and vice versa.