Ok, so as we close in on the finale, & it seems we're certain to have an impactful death be a part of it, I'll post my thoughts.
Characters who I think we just cannot do without in the final season: Dustin (unquestionably) Mike, Will & Lucas. I just don't feel like this show will play out right if any of them aren't there at the end, having gotten through all this together. No matter what's transpired, they are the core, even still.
Eleven. If she is going to die, I don't feel like now is the right time for that. Hopper. I mean, killing him off now doesn't work after last season's cliffhanger. He'll have to go beyond this. Robin. I mean it's feasible it could be her, but I've come to feel her presence adds something necessary to the show. More than anyone not in the core, her personality would be too sorely missed imho
Characters who we could manage without, but will be a really painful loss: Steve, Jonathan, or Nancy. I feel like we'll see something of an understanding about the love triangle resolved, at least a little, but the most killer way for it to go down is for one of them to die. My preference would be Nancy. That shit would ROCK the show to its knees.
Erica. I doubt it's her, but there's ways to do it, that could be powerful. Murray. While I sort of feel similarly about him as I do Robin, losing him could serve some use. Max. I feel like we're being led along to think it'll be her, but probably not, & I think she ought to make it through this, but done right, it could work too.
Joyce. Yeah. That. That might be the hardest gut punch they could workably throw us, but they could throw it.
Characters I think could die, & maybe ought to, but aren't the big one: Brenner or Owens. Possibly Eddie.