Psychopathic, insane, murderer, discrete, chill, silent, calm, hot, likes to read, powerful. He became insane by all the resets and genocidal routes repeating in loop, and he was the only monster remembering. He decided to kill all the underground by himself  in desesperation to avoid the human to do it again, and to win XP to defeat them for once. Sans knows all the AU'S, and is from the Bad Sanses squad, Schizophrenic, maniacal, spareless, desesperate, traumatized, hostile, possibly depressed.