Undertale - Yeah I'm going to take your word for it

Something to consider; Sans isn't trying to kill you. He pretty much can't thanks to your reload powers and he knows it. He's basically trying to make you ragequit, saving both you and the world in the process.

Kind of ironic in that way; Sans tried to stop the player from destroying his friends, while the only reason they're even doing it is so they can fight him.