Curate, connect, and discover
Does Dust think that the bad Sanses would be selfish? Is there a reasonable reason for him to join the Bad Sanses in some versions? He killed his entire underground thinking it was a more merciful kill than them having to go through the constant resets and he couldn't take it anymore before losing his mind. I think just making him stereotypically "psycho" doesn't give him the justice I see much of. I think the idea of taking away the happy endings of others is impossible for him, especially in specific timelines. I think that the versions of each Bad Sans having their own reasons would be fun, like how I imagine he could've been convinced by Pap to go in order to not Starve.
Don't even get me STARTED on Saint, either. He, in my opinion, joins the Bad Sanses to provide safety and food for the underground. His whole character is defending and caring for the underground despite his rough edges. It's not like he would abandon his brother and village when they're victims of fate and cruel circumstances. The idea that Killer killed everyone to just FEEL something? At least there's some level of understanding for Dust even if he also would dislike him. I've always seen Saint as a character always wanting to protect the weak, or at least protect helpless monsters in bad situations. That could lead to a whole way of him bonding with Dust for that matter
If I'm to think of Killer in the way everyone™ in the fandom sees him, he would have the least justification.
,,,,BUT WHAT IF I THINK OF SOMETHING A LITTLE DIFFERENT?
What if Killer decided to join the human to try and stop the resets like Dust? That his method wasn't just to "stop feeling awful" or to "feel nothing at all." I think Sans as a character is very fascinating, and I like to personally think he would pair with Chara as a way not to stop Frisk, but rather to stop the player. It would be interesting to think a part of Chara and Sans are fused into a soul rather than Killer y'know,,,,killing them. I don't care for the evil Chara interpretations, and I think this could lead to a more empathetic light to a character (Killer) with a really cool concept. It's a shame to me that out of all the Bad Sanses, Killer has the least justification and doesn't have that slice of humanity in him that could give him empathy from people in the community
These are just my personal takes, even if whoever reads this may think they're bad takes. Again, I LOVE almost every version someone has of a character so many people can interpret in different ways. I just like adding my own twist to try and pump more depth into each of these silly guys
Thanks for reading if you read this much of my rambling🙂↕️🫶