Okay, so you think audiences can't handle when an antagonistic character isn't completely evil. That they can't judge someone as bad unless it's bleedingly screamingly obvious. I'm afraid quite the opposite is the problem. No-one cares about the antagonist dying most of the time. It's expected it might happen and in a lot of examples people don't feel like it's consequential. They don't care. Antagonists operate like murderers or enemy combatants, morality is often cast aside. No empathy, it's us vs them. (This is my opinion but many others have expressed this idea) So I'd argue it's far more important if you want an intelligent, serious story that you give the antagonist, "the villain" I prefer antagonist myself, an element of sympathy and empathy for the audience. To make them feel like they're interesting and human and their life is worth a damn. Also your representation that romance will make people root for the antagonist is demonstrably false. People can feel more sympathetic because of it but it doesn't over-ride that the antagonist has morals the audience significantly disagrees with. The hero is always the moral choice your expected to favour, and it is usually relatively easy to make this decision.
I think you've put your side of this issue very well. I can see where you're coming from here, and lots of people agree with you. These kinds of stories are very popular. Do you see a difference between a 'protagonist' and a 'hero?' Or an 'antagonist' and a 'villain?' Or would you use these words interchangeably, when speaking about a story?
"Completely evil" is your phrase, not mine. I never once said "completely evil." You're arguing for a false dichotomy where the villain is either powerfully humanized by being shown as a loving person in a romance or they're completely evil. "Can't judge someone as bad?" Again, I didn't say that. Why? Because that's not the point. The point is who gets the support of the audience. And that person, is who is more interesting emotionally. Not who is good or bad. People care when the VILLAIN dies because they care about and like (love if the hero is really good) the HERO and the effect VILLAIN's demise has on the HERO. It's a massive emotional catharsis when the hero has been struggling for the whole story and finally wins. In a hero/villain story, the audience isn't supposed to cry for the villain. But for the hero. I remember my(and alot of people's) eyes welling up when Sauron finally went down. And that's not because we were sad for Sauron. So was The Return of the King a childish, non serious, unintelligent tale? Because that's a very snobbish position. Maybe you're one of those people who only considers dour literary works like "Far from the Madding Crowd" and "The Masterpiece" to be "serious" works and think anything "less" is non intellectual? "The hero is always the moral choice your expected to favour, and it is usually relatively easy to make this decision." Yeah because the bad dude/girl with the heart of gold who people love more than the hero is just so rare/ Sarcasm.
Let's not argue about this anymore. It's kind of consuming the thread. Oh, and when you want to do sarcasm, I suggest you use this emoticon; Just a friendly suggestion.
I would portray the lovers as deeply flawed, with a heavy bend toward the psychotic, with their love shown as not what motivates their actions, but rather it's what gives them the fortitude and strength they need to be the evil duo that might just take down the hero. Think Micky and Mallory from the movie Natural Born Killers. Watch it if you haven't.