I have the ending of my story all worked out, but it has taken a sort of turn on its own. I started thinking, 'hmmm...maybe I will change it', but I LIKE the ending the way it is, too. Should I write an alternate ending, just to see if I can, or if it is any good? It is vastly different from what I have now, sort of anti-Hollywood ending. It involves one of the MCs dying. I don't know why I keep thinking about this sort of ending. I feel like Virginia Woolf in The Hours, when she suddenly realizes: 'She will have to DIE' talking about her character.
The thing with having your protagonist die is that it requires an emotional impact. It has to be fully satisfactory of an ending too as it'll just upset the reader, in a negative way, about how they feel about your book,. It would either be they wasted their time because the story was pointless due to the protagonist dying òit was so stale thatit became an "oh." moment. I'm sure other's can explain this better.
What kind of story do you want to tell? What ending feels right to you? Which one makes the story say what you want to say? Which one takes the reader where you want the reader to go? This is where the rubber meets the road, as they say - where we prove our chops as a writer. It's the difference between writing for self-amusement and writing for publication. When we write for our own amusement, we never quite leave the role of the reader, and so we are writing to find out what happens because that's what we do when we read. But when we write for others, we are writing so that they will find out what happens. That means the writer is in control of the story, not the reader. There's nothing wrong with writing an alternative ending to "try it on". When I finished the first draft of my current project, I was in love with the ending - great ending! But as I started to edit, an uncomfortable thought welled up in me - my great ending didn't fit. It was a shiny tailpipe on the wrong car. So, I rewrote it, not to try it on (that's really what I'd done with the first ending, if I'm honest about it), but to stay. The particulars still need tweaking, but the thrust of the ending will stay.
^this. Although I will say that main character's dying has no more shock value for me anymore, perhaps that's because I used to play video games a lot where they just died left right and center, but I normally wonder when the main character is rather than if they will die. Something to take in consideration, but as @EdFromNY says, you just gotta go with what seems right. Definitely test out the alternate ending, and ask people who've read the whole story for their opinions.