Ragnell posted last night asking whether something she'd written previously in regard to the Green Lantern refrigerator scene comes across as a justification of the trope of harming members of the supporting cast for the purpose of developing the hero. I said in comments that I didn't think that it did, because the trope really can't be justified, and I promised to elaborate further here because my reasons for saying it are so complex and multifaceted.
*edit* not as much as I thought they were, as it turns out*
The first thing is that I don't think it makes a whole lot of sense. More accurately, it does and it doesn't. Starting from the end goal and working backward through the events, as Ragnell does, it almost works. The goal is to develop Kyle as a character by in this case putting him through some of the risks involved in being a superhero, and to get him to make a break with his old life. Another goal is to show how nasty the villain, Major Force is. Working backward, a common way of doing this is to harm a loved one. So we create a loved one, and give her a fairly developed and likable personality. The villain drops some hints, shows up while the hero is out, there's a struggle, then the hero returns to find the girlfriend dead. It hits the beats and solves the puzzle. But...does it solve the puzzle well?
This is where I have to say no. Like I said, starting at the goal and working backwards, it kind of makes sense. There's a sense that things have to happen a certain way in order for the end goal to be realized. Working forward, though, it really doesn't make much sense at all.
The main problem is with the villain's motivation. Why does he want to hurt the hero at all? Does he see Kyle as an obstacle to his primary goal? Well, given that in this case his goal is to get the ring that's on Kyle's finger, I suppose he is an obstacle. So why not just go after the hero directly and try to kill him, rather than hurting the girlfriend? Somewhere along the line there has to be an indication that there is greater value in going after the girlfriend than in going after the hero himself, and that there is greater value in killing her than in, say kidnapping her (on this point I'm a bit confused. Is he supposed to just be a general homicidal maniac, or just a somewhat unstable government agent?). If the villain is thinking "I'll show him it's dangerous to mess with me," well, that kind of fails in that it wasn't particularly dangerous to the hero. When the deed is done, he still has all of his totally rad powers, and now in addition he has become an even bigger obstacle to the villain's goals because he is pissed off and has a personal stake in stopping him. If the goal is solely to get the ring, Major Force's actions don't make much sense. If the goal is to demonstrate his threat level, he kind of fails there, too. He's just another in a long line of super powered people who has murdered a non-powered person, which is pretty unspectacular. In the end he has demonstrated that he is mean and willing to kill people, but we already knew that. He's willing to kill Kyle, too; he just happens to fail at that.
Now, stepping outside of this one specific story to look at the cliché in general, the point of the villain's motivation is where it most often falls flat. Hurting the hero's loved ones is never going to stop the hero from ruining the villain's plans. So while from an extra-textual perspective it may satisfy the author's plot requirements, intra-textually it doesn't satisfy the villain's goals, and in fact often works against them (this is not such a big deal for explicitly revenge-motivated villains, like Venom). Now, some villains work against their own goals all the time and don't even realize it, but the text knows, if that makes sense. It's sold to the reader. When villains go after the heroes' loved ones, they may accomplish something for the writer, but what do they accomplish for themselves?
The other element that makes the convention a problem is the girlfriend. She is a character, and so presumably she has an arc of her own, which generally culminates with her death. Again, extra-textually, we know it's really about the hero. His name's on the cover. He won't be dying or getting permanently injured, and everything that happens in the book is his story. But inside the text, she is the victim. It's important to know that her death is necessary for her arc. There needs to be a purpose for her arc to intersect with that of the villain other than just "we need her dead so the hero can be driven to the edge." Otherwise it's just a plot point, and she, rather than being a character in her own right, is really just an extension of the hero. Killing her becomes the equivalent of cutting an arm off of the hero or something. She doesn't really have a purpose of her own; she doesn't need to be there. That's lazy writing. There's nothing particularly sexist about it until we contextualize it, until we realize that it exists in a world in which women really have been seen as appendages of the men in their lives for a very long time.
So kill away, writers, but keep in mind how and keep in mind why, is what I guess I'm saying.
Also, to answer the question that Ragnell actually asked: no, I wouldn't consider that paragraph a justification of the phenomenon. There's a difference between explaining the logic behind an instance of the convention and justifying it even in itself, let alone the entire phenomenon.