Me and my girlfriend were watching Harry Potter and the Order of the Phoenix the other day, and when Sirius Black died we both took note of how strong our emotions of heartbreak were for both the character and Harry. I update her on my current book frequently and one thing that she noted was that while some characters I've introduced have died, none of them are very connected to the reader, (non-main characters). She said that if I killed a main character that it would have a strong affect on the reader and that it might be beneficial. I'm on the fence because I really like all my main characters and plan to build on them all, but I do love to twang on a reader's heart strings and put them on an emotional roller coaster. Any thoughts or opinions on killing main characters?
But the point of writing is not to kill off characters but to entertain. You can tell just as engaging a story with characters who are still breathing than telling a story where someone dies. Like, Han didn't have to die in the force awakens in order for the audience to be emotionally invested. Han was there and that was enough. The writers did their job (fan service). I won't speak on the travesty of the sequel trilogy here as many others have already and are much better at articulating the general consensus of fans that it's utter trite.
Understand that there just needs to be truth in what characters are doing. In the subtlest or grandest of ways make their actions, motives, beliefs or lack thereof clear to the reader. But the truth in fiction is the human element, good or evil. It will shine through and readers will react.
And if you really like your characters, expose their dirty deeds to the reader in hopes that the character will acknowledge them and commit to being a better human being. Treat your character development over the course of the story like therapy for the character. Let them come into a little bit of shame when their flaws are exposed, then give them the opportunity to make better choices.
And remember, if progression is organic, it won't be the author killing off characters, it will be characters killing characters. Your job will be to rationalize the act of killing in the character's mind. You plant the idea and let the potential killer follow through with the act if they so choose.
In fact, what would be just as tantalizing to the reader is if someone is moments away from death but the killer stays his weapon and the almost murder victim is never made aware. Or, maybe they find out ten chapters later that someone lurked in the dark ten feet away with the intent to do harm. Or perhaps there's a scene where fate seems to push a character out of a deadly situation. When the character is removed from the hidden danger, the danger is exposed and the character is shocked and relieved and becomes an emotional wreck.
What I'm getting at is maybe put your characters in grave danger after their value to those around them is well established, then pull them to safety.