Betrayer -> Killer

Inspiration: Blood World (Violet)

Due do his constant reach to the surface of the monsters and the humans were in peace, the turns over the university of the land to use his knowledge, right after Chara was making something with black poisonous inside his food before he ate it before he vomits and ended up in a coma into the hospital, strange dream what Chara rejects the deal with him to his betrayed by Frisk.

Then, in the reality, something changed.

Even with his black right eye on his hate, everyone in the people ignored him and even Frisk to betray him, Papyrus wasn't ignoring that he cared for him, until one night, they killed and tortured Papyrus at the scene of the report, and Sans can take this anymore, he got bullied by his emotions to himself to their unusual words before this is not a dream to cut himself, and he WILL REGRET THAT HE WOULD ACCEPT THE DEAL UNTIL HIS SOUL GOT A LITTLE FRACTURE AND DETERMINED.

Sans decided to kill humans and monsters and commit arson to the humanity, he burned the schools, stores and many more to cause trouble to the building, and when he puke on his black substance again and again, before he was a sadistic scumbag to everyone else.

(I'm so bored to do lore rn, I'm lazy. -^-)