I feel how you do about real life killers, if I had my way we wouldn't even know their names or faces anymore. Fictional serial killers and fictional victims are another story, and I feel like you're blurring the line between the two here when there is a distinction.

It sounds harsh for characters that already had the worst happen to them but it just feels like outright lying to pretend the most major thing that happened to them wasn't their murder. Nothing in a victim's story is going to outweigh what their fate was, everything will then be colored by their demise, everything will seem sadder. Saving it until the end is just disingenuous and cheap really, like their entire life amounted to a gruesome twist ending.