Deltarune Chapter 2’s… alternate route is… *fucking **dark.***
You end up willfully corrupting Noelle into being a killer, growing strong, via basically emotionally/mentally abusing her into submission, eventually using “Snowgrave” to kill Berdly (Snowgrave is explicitly said to be “FATAL” in the menu, and in the Light World, Berdly doesn’t wake up during the epilogue) when she’s wearing an item that gives the Trance effect (and she tries multiple times to resist that order), and it’s heavily implied she goes on a killing spree after that, after leaving you, due to how the castle is more… empty, how Spamton took over.
You thought Undertale’s Genocide Route was awful? Well, twisting another character to kill because you can’t, via their powerful freezing magic is worse, in a way. Most enemies try to run away in terror, instead of encountering you, so you chase them down. And the worst part is, you can further twist the knife with Noelle in the Epilogue.
And no, it’s not Kris doing this, it’s you compelling them to do this, with them both on the strings. It’s indicated Kris looked hurt, by the other two, when they reunite in that route… and it’s noted by Noelle later that the voice didn’t sound like Kris’…
Even Ralsei, who has many oddities in his own right, seems on some level disturbed/uneasy by how he doesn’t have control like they do normally, in trying and failing to get you to switch to Susie’s POV.
Also, instead of fighting the Queen, you have to fight the chapter’s hidden boss solo at the end, and the outcome of that fight is… something.
So, your choices don’t matter, as they said? You can, seemingly, still fuck things up, by manipulating someone whose choices actually do matter, egging them into doing something ala Chara and Asriel.