in one of the undertale timelines Sans experiencing much trauma from the psychopath human he snapped he wants justice brought down apon this human and will do tricks on them to get them to die but since they dont fear death he will cause much pain to them as possible, in one of the resets the human had killed his brother and fled, Sans being there was blamed for the killing of his own brother but since sans was in shock he had no words, the royal guards where called to investigate the situation, he told them to get out of the way and he will finish his buisness with the true monster. but the guards obviously had no idea what he was talking about and fought back as sans killed the guards out of self defense it looked much worse on him, Undyne came and fought against him, she damaged him up pretty badly and cracking his skull he ended up passing out, they had him patched up, they saw the results of his injuries seeing he had severe head trauma, making him much different then he was before. so when he woke up he was a much different person. he regained his strength from the stuff they where giving him, but he was chained up. undyne investigated him. all he could do was laugh and make up nonesense, Undyne was mad but refused to hurt him. when she left the room, Sans took this as a moment to escape, he remembered his main goal but this time he wont let anyone get in his way. as he killed those who stood in his way his lv raised, as he once said himself. the more you kill, the easier it becomes to distance yourself. the more you distance yourself, the less you will hurt. the more easily you can bring yourself to hurt others.
