Kylo’s eventual fate is a very tricky thing, especially because of the context the ST has set up.
I mean, if he dies, it’s boring. Die evil? Ooh, how original. I’ve
never seen a bad guy die at the end of a movie before.
Die redeemed? Oh... so he really is just Diet Darth Vader: less taste, half as filling.
At the same time, you can’t really give the character a happy ending, not because there’s some philosophical issue with it, but because the character is incapable of having that and it remaining dramatically satisfying. When the character killed Han Solo, maimed Finn, and violated Rey’s mind, he pretty much ensured that a bittersweet ending was the best he could manage for himself.
And if it was *just* Kylo’s own fate at stake, I’d be satisfied and even excited if they were going to give him and “Ulic Qel-Droma” after from the old Tales of the Jedi comics: go into exile/be marooned and take the long road back to redemptio, eventually succeeding in future media.
But...
If he’s the only Skywalker left, than we have some more issues.
Because that means that since Kylo can’t really have a happy ending,
neither can the Skywalkers. I mean, right now? The Skywalkers are a Curse on the Galaxy. No ifs, ands or buts; Kylo undoes all the heroic actions taken by Leia, Han and Luke and even renders Vader’s redemption kind of a lost cause. It’s the natural consequence of a) making Kylo a lesser repeat of Vader, and b) making him the only generation 3 Skywalker. The OT ending in ROTJ ends up becoming just a pause between only nominally different evil-doers murdering millions left and right.
And if you try and make an exception for Kylo to try and help the Skywalkers... congratulations! You just rejected the very reasoning you had for making Rey and Random, and basically having the story give him special treatment and favoritism just because of his family,
probably at the expense of Rey and Finn, and in a manner antithetical to the idea that his sense of entitlement is one of his biggest flaws.
Right now, Kylo’s too underwritten and lonesome to provide a rewarding ending for his family, implying he should be killed if they just want to move past the Skywalkers... but that gives you a depressing ending for the family and a boring ending for him.
I’m just saying, it feels like we’d have a lot more options if Rey were a Skywalker...