Killing off movie characters that audiences have become attached to is always a risk. If it's not done properly, you can leave fans feeling burned about ever investing in the franchise to begin with, removing the elements that made them care at all in the first place.
While plenty of writers and directors have gotten this right over the years, creating movie deaths that have stayed with fans for decades, one sure-fire way to cause an upset is to kill them off in between sequels. It's bad enough when characters are taken out off-screen, but when they're murdered between movies, it feels like a personal slap in the face.
Even then though, some films handle this better than others. Because sometimes it's clear that an unceremonious, barely-mentioned death is given to characters that filmmakers want to pretend never existed in the first place, or because they want to deliver a petty, middle finger to either fans, or the actors occupying the role.
Whatever the reason though, it always feels a little insulting, and like these creations were robbed of a proper send-off.