This theme is pretty common to fiction. It's not always specifically in the "boy meets girl, boy loses girl, boy kills girl in a fit of vengeful passion" mold. Some times it's "girl loses boy, girl kills boy" or "boy kills boy who stole girl from him". And of course, there are non-lethal variants on it. But the theme they all have in common is the notion of exacting vengeance for an unrequited love.
I dislike this theme rather intensely. Often the character whose love is unrequited is presented sympathetically, as a tragic hero like Othello. Sure, he's not doing the right thing when he offs his wife -- but he's doing it for love. That makes it understandable, doesn't it?
Yeah, sure. Personally, I think it's a pretty poor sort of love that can't stand to see the loved one happy -- even if that happiness is found with someone else.
I've long recognized that I hate this portrayal of "true love" as selfish and greedy, caring only for possession and more than willing to destroy if they are denied it.
But what I just noticed today is that, in my own fiction, I very commonly invert this trope. My characters, even when badly hurt or spurned by their loved ones, continue to act in the best interest of those loved ones. "Yes, I've been betrayed," they say. "But I still want her [or him] to be happy." In my mind, that's what it means to love someone. You do what's best for them, regardless of what they do or don't do for you.
Still, it strikes me that, while I believe that, plenty of people do behave in the opposite way. Realistically speaking, different characters should react in different ways, and some of them ought to lash out dangerously. Infatuation, if not what I consider actual love, can easily turn to hatred.