Even thou thet players are the ones to blame on , chara still participated on the genocide so in reality they HELP the player to get to their goal because when we kill sans we aren't in control of our character/frisk anymore on that point. chara takes control and kills the two survivors left (asgore and flowey) remember when we meet chara and she says the following:

"I'm the demon that comes when people call its name"

"everytime a number increases..that feeling...is me"

"Power"

So the power of destruction represents her (because she's a demon child) she may have not ask to do genocide or know about it but needed LOVE to be reborn as a recantation of her formal self



So in true here chara is also apart to blame here