Azazel

Azazel was a powerful demon and a Prince of Hell who served Lucifer. Until Sin City, Azazel's name was not revealed and he was referred to by nicknames such as The Demon, The Yellow-Eyed Demon, or Yellow Eyes.

Early life
He was eventually chosen by Lucifer to become a Prince of Hell alongside Ramiel, Asmodeus and Dagon and was transformed by Lucifer personally and became one of the first four demons created after Lilith, and Married to Lilith having children: Arras,  Alex, Josephnie, Marcus and two bastard childern: "son" known as Viserys and a "daughter" known as Hela. As a Prince of Hell, Azazel was a demonic general and was fanatically loyal to Lucifer to the point that when the other Princes gave up on Lucifer's plan and left for Earth, Azazel stayed to rule Hell and free Lucifer to start the Apocalypse. At some point, Azazel left Hell and went to Earth to search for the entrance to Lucifer's cage.

After years of searching, Azazel finally located the doorway to Lucifer's prison in 1972. The fallen angel tasked him with freeing the demon Lilith ( his wife) from Hell, as she was needed to break the 66 Seals holding Lucifer captive, and also to find him a "special child" strong. By the following year, he began making demonic pacts with young individuals - specifically young women - in exchange for a wish: that he would be allowed to enter their homes exactly ten years from when they made the bargain. He promised that no harm would come to them as long as they did not interfere with his business.

Personality
Angry and vengeful over his own eternal damnation, Azazel took pleasure in inflicting pain (whether psychological or physical) onto others. Having a sadistic sense of humor, he liked to play with his victims' emotions by convincing them that their worst fears were true before he killed them. His signature method of murder was exceptionally vicious: he telekinetically pinned his victims to the ceiling, slit their stomachs open and burned them alive while ensuring that their husbands witnessed their death. Strangely, unlike many demons, Azazel rarely killed when it was unnecessary, as he does not kill the parents of his special children when they did not interrupt his blood rituals and even states that Mary's death was simply bad luck.

Powers and Abilities
Azazel was a very high-ranking demon, described by Amelia as one of two beings on the "A-list" of demons (the other being Lilith) he remained the only known demon with yellow eyes. Azazel ranked incredibly high in Hell's hierarchy, being an heir to the throne of Hell and led the plan to free Lucifer. The demon Casey described him as a tyrant who held the demons all together, saying, "When you did him in, it all fell apart." He was a considerably powerful demon, one of (if not) the most powerful to appear on the show along with Lilith, Cain, Alastair and Abaddon who was a Knight of Hell. Azazel was eventually revealed to be a Prince of Hell, one of the very first demons ever created and a demonic general making him very powerful indeed.
 * Demonic Possession - He often possessed humans to manifest, though on one notable occasion he possessed a reaper - a feat that has not since been accomplished (on-screen) by any other being. His hosts tended to be older white males.
 * Super strength - He enhanced his host's physical strength to a superhuman level, to an even greater extent than all other demons do (With the exceptions of Cain and White eyed demons.
 * Advanced Telekinesis - He could move people and objects using only his mind. He was very skilled with this ability.
 * Biokinesis - He demonstrated the ability to psychically injure humans, even inducing fatal internal bleeding with a mere glare. One of the omens of Azazel's arrival also included mass cattle deaths.
 * Pyrokinesis - He could generate and manipulate fire. His power over fire was extensive enough that he could render entire buildings ablaze in minutes or even seconds.
 * Immunity - As a Prince of Hell, Azazel was immune to most demonic weaknesses, including holy water, salt, holy ground, and his brother Ramiel is shown to also be immune to the demon-killing knife, devil's trap bullets, and angel blades, so it can be concluded that Azazel was as well.
 * Invulnerability - He could not be harmed by conventional weapons or methods, gun blasts and flames barely affected him.
 * Immortality - Azazel was able to potentially live forever, he was thousands of years old when he died.
 * Teleportation - He could travel instantly from one place to another including hell and earth without occupying the space in between, he was quick enough to use this to avoid bullets.
 * Weather Manipulation - As great masses of demons can, Azazel's presence alone could cause thunderstorms, massive temperature fluctuations, and sudden gusts of wind.
 * Electrokinesis - His mere presence caused lights to flicker, electronic devices to go haywire, and clocks to stop.
 * Super senses - Was able to tell Dean wasn't one of his special Children, simply by smelling his neck.