Lucifer

Nigh-Omnipotence - Being the second oldest archangel, Lucifer is incredibly powerful. As only God and Death can defeat him with certainty, Lucifer has incalculable supernatural power. He can even slay ancient pagan deities with ease, despite using an imperfect and decaying vessel. With Sam as his vessel, he can use the full extent of his powers. Unlike most characters, the extent of his powers is not limited by his presence, as such giving them a near infinite range.
Immortality - As an angel, Lucifer has an infinitely long lifespan. Time does not degrade his vessel, like with all celestial beings. He is among the first angels and is therefore older than the Earth itself, making him well over 10,000 years old. The excessive passing of time does not degrade his vessel, like with all celestial beings. His vessel is unaffected by diseases and toxins. He does not tire, and does not require food, water, oxygen, or sleep to sustain his vessel. On one occasion, Castiel clearly says about killing Lucifer, "It's foolish, it can't be done", and later calls the task "insane". However, an archangelic blade can kill him, as can God or Death.
Angelic Possession - Like all angels Lucifer is required to use a vessel on Earth, as Zachariah emphasizes. And he needs the vessel's permission, as with all angels. Because of the immensity of his power, he must use a vessel descended from Cain or Abel, or it will begin to decay.
Invulnerability - Lucifer's vessel is impervious to damage and injury, except when harmed by an archangel blade, God or Death, supernatural weapons of significant power, or his archangel brethren. Kali, the most powerful of the deities at the gathering of the pagan deities, tried to harm him with a pyrokinetic attack, but it had no effect and Lucifer simply smiled at her attempt at harming him, showing him to be unaffected by extreme temperatures. The Colt caused him initial pain, but he soon recovered, though it should be noted that his temporary vessel was decaying at the time.
Immunity - Lucifer is one of only five things in creation that the Colt cannot kill.
Cosmic Awareness - Lucifer has immense awareness of everything, as Sam has said, "I'm sure he knows a buttload we don't". He knows spells capable of binding the Horsemen to him, but he, according to Chuck, didn't know about the Impala.
Superhuman Strength - As an archangel, Lucifer endows his vessel with immense superhuman strength, sufficient enough to having slaughtered ancient pagan deities with his bare hands with minor effort. As Gabriel predicted, Lucifer "turned them into finger paint." Lucifer went on a rampage during which he brutally ripped the other gods to shreds, beating them to death and tearing off their limbs through sheer force. He was able to knock out Kali with one punch, sending her into the air and across the room. This makes him among the strongest beings in all of existence. As the second oldest archangel, he's significantly stronger than any other angel as well as all demons, spirits, humans, and earthly monsters, including the alphas. He was also able to casually overpower his younger brother Gabriel, an archangel like him. Humans are powerless against him in terms of physical might; he once effortlessly threw Dean into the Impala with great force and literally beat him to a bloody pulp, nearly killing him. Only Michael is his certain equal and possible superior in strength.
Super Stamina - His vessel is unaffected by diseases and toxins. He does not tire, and does not require food, water, oxygen, or sleep to sustain his vessel.
Regeneration - If Lucifer's vessel receives any physical damage, the wound will completely heal instantaneously. When shot with the Colt, for example, the bullet hole healed in under a minute. Interestingly, the ability does not reverse the decay caused to Nick by Lucifer's power. Lucifer is unaffected by natural diseases and illnesses.
Shapeshifting - Lucifer can change his form regardless of being inside a vessel or otherwise. Lucifer can change his shape into any person he wanted, similar to Gabriel's ability; Lucifer once took the form of a Reaper to lure Castiel away.
Teleportation - Lucifer can travel anywhere instantly without occupying the space in between. However, when imprisioned in his cage, he cannot leave unless it is opened by an outside force.
Power Negation - Lucifer could prevent lesser supernatural creatures from using their powers, as Baldur and Kali where unable to teleport either themselves or the Winchesters when he arrived at the motel where they were hiding.
Telepathy - Lucifer had complete access to Sam's memories, thoughts, and emotions while he possessed him. Lucifer describes Sam's mind as a "grapefruit."
Advanced Telekinesis - Lucifer can impart kinetic energy on matter with his mind. He is extremely proficient, being able to rip pagan deities apart with this power.
Dream Walking - Lucifer has the ability to enter a person's dreams. Even without a human vessel, Lucifer was able to speak with Nick in his dreams while taking on the appearance of his deceased wife. He demonstrated this again when he spoke to Sam in his dreams while taking on the appearance of Jessica Moore.
Cryokinesis - Lucifer can manipulate and generate cold. He froze a pane of glass by merely breathing on it.
Supernatural Perception - Lucifer can perceive the true form of beings invisible to the human eye. Lucifer was able to see the true form of Death when he raised the Horseman out of his prison.
Weather Manipulation - When Lucifer was released, he altered the weather by creating severe winds and causing hurricanes and tornadoes across the world. He made the entire city of Detroit's temperature drop simply through his presence.
Biokinesis - Lucifer killed Castiel by speeding up his molecules to the point where it caused him to explode simply by snapping his fingers.
Reality Warping - Although never displayed in person, Lucifer reminded Gabriel that he taught him everything he knew about using this power, when the latter tried to use it to kill him. Upon his escape the Koreans made their first successful nuclear test.
Spell Casting - Lucifer was able to bind the Horsemen to his presence with a spell, controlling their actions to a moderate degree. He also performed a ritual sacrifice of demons to release Death from his coffin. He also knew how to ward angels from the Angel Tablet.
Resurrection - Lucifer can easily revive dead people. He is also said to be able to bring back deceased angels. In The Devil You Know, Crowley noted Lucifer can also resurrect dead demons.
Terrakinesis - Lucifer could generate earthquakes through his mere presence on the earth; he was able to cause them at a colossal range, creating several across the whole world while he was in America.
Precognition - Lucifer could see and accurately predict the future, but he could not see the whole picture; he knew he would possess Sam in Detroit and told him the first time he met him.
Torturing - Lucifer is skilled in torture, both physical and spiritual. He tortured Lilith's spirit to the point where he turned her into the original demon. He also tortured Sam to the point where the mental damage would have killed him, had Castiel not absorbed the damage.
White Light - He once captured Castiel by disabling him with a burst of white light.
Psychic Projection - Despite being trapped in the cage, he could still communicate to beings on Earth, as he did with Azazel, though Azazel had to sacrifice several nuns for this to be achieved.