I believe in the “chara is not the bag guy” theory with a passion.
And honestly, my au doesn’t have a player character in it either. Because in my au it isn’t really a game? It’s sort of just their reality, with game elements but it’s not a game in their universe if that makes sense? Idk, it just feels like it cheapens the experience if it’s just a game and that sort of stuff is something I don’t want to get into.
But that aside, if there is no player character in MY version, and Chara is not the genocidal bad guy, whose fault is it for the genocide route? Well, my answer is simple: Frisk.
Now, of course I’m not saying they are a bad person, or even that they meant to cause such severe harm, but they are a child whose main trait is the determination to push through any challenges and make things HAPPEN. I’ve always interpreted them as being a very curious kid, and one that is drawn to pacifism. But they also have the power to set back time, over and over again and see every possible outcome. They at first used this power to replay the adventure with their monster friends over and over and over again, but doing that so many times would become boring eventually.
They wanted something new. They wanted to see something different, just like Flowey. And just like Flowey, they went from befriending the monsters over and over again to slaughtering the monsters over and over again. Just to see what would happen, to test the limits of their friends, and because they wanted to see all aspects of their friends.
This is true to the souls as well. At first, Frisk wanted to be their friends, find out more about them, and re-entered over and over again to see new things. They were drawn to it, because the souls and their new realm were something DIFFERENT. So they reset and see if the outside affected their realm, killing monsters to see if it affected the kids, and eventually killing the kids to see how it would effect the outside world. They didn’t really mean to do so much harm, though they were aware of the consequences of their actions. The kids can remember, the kids can see when they reset in their realm because it’s highly magic sensitive. Even if at first they didn’t understand the feeling and what it mean, they do now, and can remember basic gists of Frisks’ previous visits.
And part of Frisk feels bad for this, because the kids can remember the hurt they were put through and most struggle and be confused as to why. But it also feeds heavily into their curiosity. Because since they remember snipits of previous runs, their behavior changes in the next one. In the first genocide run, Paige was alone on the balcony playing with her toys when she was attacked and killed. But the second time around, Paige had some sort of memory of getting injured by someone while playing alone on the balcony, and thus decided to build snowmen with Bentley instead. This changes the order that a genocide would go in, as Bentley would be the first to die and Paige would likely get away while normally she dies first.
Frisk struggles with feeling bad for them and feeling fascinated by the possibilities. These kids remember, but not enough to remember that Frisk is the cause of all of it. So it’s easy to assume that they will never catch on to what Frisk is doing, because they don’t understand how the power of Determination works. So it feels like a win win to Frisk, who can continue to experiment without leaving any lasting harm to their friendships.
This is why there are SO MANY VARIANTS to the genocide route with these kids. Actions of previous routes shape behavior of the kids in upcoming routes, so the order they appear is rarely the same.
But in the end, they WILL find out eventually. They will piece it together seeing more and more fractured memories of deaths that have yet to happen, and they will gradually lose trust in Frisk because they are the only outside factor that could be causing this. Eventually Frisk will have to deal with the consequences of their actions.