Why would you ever want to fight this guy more than once? Freak is right.
There's guy which posted sans no hits battle on youtube. And his comment? ,,When I slowed down battle from x1,5 speed to normal, battle seemed TOO EASY!"
Hohohohohohohoho, what a freak.
The best thing? Sans dialogue DOES change when you off him several times.
It's darkly ironic, isn't it? The whole reason Sans fights you time and time again is to stop you from getting the Genocide ending. But because his battle is so challenging and awesome, many people take the Genocide route only to fight him, which completely defeats his purpose.
*raises hand* Exactly what Ikaros said, Sans' mission is to stop Genocider Frisk, but because he's so damn hyped in both his fight and his music, a ton of people run genocide just to fight him for themselves!
Though, I'm glad that even if the Genocide Route is largely discouraged morally, the player is still provided with an awesome experience no matter what path they choose that actually fits the path. Pacifist nets you a feel-good story boss that you technically can't die against (still fun to "fight" nonetheless), while Genocide gives you bosses that are genuinely challenging, even if few, and all routes provide excellent narrative. Truly game of the year, all years.