Copper as Killer!Sans.

Lore:

Halfway during the episode of Red Snow, Rinny has decided to kill and torture all of victims in the cabin along with Elma's friends, except for Copper.

They will calling him after join forces among them to take down Rinny, putting atrocities during against ruining their society, and Luny will take care of Rinny by herself.

Bloon was just mocking Copper for his misery of their ego, before Copper had enough of him before punching him really hard.

Copper had a nightmare during she was killed by him over and over till it finally ripped apart, making it won't go away further and cutting himself to stop mocking.

He decided to kill Rinny on his own to betrays the law to using electrical powers against her, but it didn't work, she shot both his limbs off, but eventually Copper uses again to kill him, and he did it. Everyone's friends were cheerful. In his mind of Copper's thoughts, Rinny had to deal with him, and uses him as his control and locking him away from his thoughts. Giving his sadistic look, he strucks four of them with his red lightning bolt before they were dead except for Bloon. He enhanced his full power of fatal electricity. He confronts Bloon to mock him and betrays him after he was getting tortured and died. It ended in this episode, Rinny and Copper fuses together into one of them all, he named Masochist. He rushed to find the stuffs so he can stand, walk and hold again. Until he found a bionic mechanical arms and legs to use to fly and blast really high.

The arms could change into a different torture weapons.