Honestly, I don't think Toby Fox would like it much. Sans is putting in way too much effort for a lazy guy, and Chara vs Frisk is kind of missing the point, in that it's the player who push's both of them.
So, post Genocide route question: [SPOILER - highlight to read]: Does the photo of Chara and the crossed out faces mean everyone dies at the end of true Pacifist? Or is it just the game taunting you with "Remember this? Yeah, that still happened."
Tbh, I think I can safely say I have nothing to prove, since I deliberately took the most difficut path through neutral. No healing items (Only broke that for the butterscotch pie, because it's themeatically appropriate, dammit!) No armor changes.
Including refusing to accept a pass on Papyrus. I was going to beat him, no matter what.
And he was both the most fun I had with a boss, and the hardest. But that "congratulations" from the Annoying Dog/Toby Fox made it all worth it.
Chara and Frisk share the same body, so kind of hard for them to fight.
I've seen the genocide route. Sans only fights when everythings about to be destroyed. Outside of that, you can all the main monsters, and even his brother, and he won't do more then send you a phone call telling you to go to hell.
You are not Frisk, this is made abundantly clear when Flowey addresses you at the end of the True ending. Frisk is a person with his own personality and feelings, it is entirely the player that forces him to murder, this also being what corrupts Chara.