Board Thread:General Discussion/@comment-36432399-20181028013241/@comment-31593032-20181028115104

Well there's the popular theory that Chara is the narrator of the game, and they're definitely the narrator in New Home at the end of genocide. It's pretty likely that Chara possessed Frisk at the end of the genocide route, and they're the ones that attack characters repeatedly without pressing FIGHT. That would mean that they can do 9999999999999+ damage to Sans, Asgore, and the player, maybe more if you think they killed the other bosses.

but hey that's just a theory