"looks like i finally managed to make things even between us, eh pal?" "..listen, i never wanted to do this, but i gotta ask, what's the point?" "what do ya gain from all this?" "...not very talkative, eh?" "fine then, seems like talkin' with ya never went anywhere anyways..."
this is the hotlands encounter. this takes place almost right after the waterfall encounter as the human won't allow sans to escape this time, but this action has somewhat annoyed sans so he has to fight them once again before he can continue his plan...