Cain

Cain is a retired demon known as the Father of Murder who used to train the Knights of Hell.

Background
Cain was the older brother of Abel. Although it was originally and commonly thought that Cain was jealous of his brother Abel, Cain later revealed that Abel was in fact talking to Lucifer. In an effort to protect his brother from corruption, Cain offered a deal. Cain offered himself to Lucifer so that Abel would go to Heaven instead. Lucifer agreed, on the condition that Cain himself would send his brother to Heaven. Thus, Abel was struck down by Cain using the First Blade. Because of this, Cain became a demon, and was considered to be the most terrible demon to ever walk he earth before suddenly vanishing. This act of killing between brothers would set the precedent of their descendants being the vessels of Michael and Lucifer, and thus, again require a brother killing a brother during the Apocalypse.

During Cain's disappearance, all other demons thought or hoped he was dead. Crowley described him to be "the best at being the worst".

Cain was the mentor of the Knights of Hell. He created the entire order with his bare hands, and also killed all but one with the First Blade. Abaddon, the last remaining Knight, possessed Cain's wife Colette, in an attempt to coerce Cain to return to his work as the leader of the Knights. When Cain declined, Abaddon killed Colette. It was during then Cain made a promise to Colette that he would retire from his work as a demon.

First Born
Cain lived life as a bee collector in Missouri. After being convinced Dean lived up to his reputation and that the hunter proved to be similar to the demon, Cain decided to transfer the Mark of Cain to Dean. He then teleported Dean and Crowley to safety after making Dean promise to return and kill him after killing Abaddon. He then took on an entire army of demons single-handedly.

Powers and Abilities
Cain was an extremely powerful demon. He could kill other demons with a mere touch. He could even prevent Crowley, the King of Hell and a powerful demon himself, from escaping and speaking just by a simple gesture.
 * Immortality - Cain is at least 10,000 years old.
 * Demonic Possession - He possesses humans to exist on Earth.
 * Super Strength - Being the original Knight of Hell, Cain is considerably stronger than lesser demons.
 * Telekinesis - He could move objects with his mind.
 * Teleportation - He teleported from across a field to beside Dean and Crowley and then to Collette's grave and back.
 * Demonic Smiting - He can kill demons with a touch similar to angels. Except in Cain's case, the color is red rather than bright white light.
 * Immunity - Cain is completely immune to the demon killing knife. Only the First Blade could kill him.
 * Invulnerability - Cain is invulnerable to normal and mortal harm.
 * Apporting - Cain was able to teleport Dean and Crowley outside with a touch.