Seven Deadly Sins

The Seven Deadly Sins were a group of seven demons. Despite only being black-eyed demons, they possessed special powers unique to themselves. Because of these powers, they were originally imprisoned deep in Hell close to Lilith, unable to escape before the gates of Hell were opened. They appeared to follow their own agenda after Azazel's death, as Pride was disgusted to think of Sam Winchester as a leader for a demonic army.

The Seven Deadly Sins
Before their release, the Seven Deadly Sins had not been on the earth since the dark ages, as such they were like nothing hunters had faced for hundreds of years.

In 1589, Peter Binsfeld realized they were not just vices, but had physical forms, as such he wrote them for the first time as demons.

Upon the opening of the Devil's Gate, they were released after which point, they began to have fun and celebrated their freedom by using their powers to affect humans. After a skirmish, they were all either destroyed or sent back to hell by Dean and Sam, with the help of Bobby, Tamara and Ruby.

Envy
Claimed that they are not sins but actually "natural human instinct". He possessed the human from Oak Park Chicago Walter Rosen. He approached a shopper at a clothing store using the persuasion of envy towards a female's shoes which led her to fatally smashing the other woman's face on the windscreen of a red car, after which she stole the victim's shoes. Envy's visage was captured on surveillance cameras and seen by Dean, Sam and Bobby. He was then tracked by Dean Winchester and found to have eaten at a small bar.

Dean, Sam and Bobby stake out at the bar until Walter arrives and enters. Dean and the others are halted when hunters Isaac and Tamara enter "half-cocked," as described by Bobby. Isaac then attempted to enter the restroom following Envy, but was subdued by Wrath which brought Envy back to watch the hunter's demise. Envy was then broken in by Dean, Sam and Bobby. He successfully dodged their splash waves of holy water and advanced on Dean. Dean pushed Envy into the devil trapped boot of Bobby's Chevette and took the demon along with them back to Isaac's house. Envy was then subdued in a chair underneath a devil's trap. Tamara performed a violent exorcism after hearing Envy's speech and taunting. Although successful, the rite caused Walter to die in the process as the demon was determined to cling to its human host.

Lust
She possessed a beautiful girl, and due to her nature, she was in a constant state of lust, more willing to have fun with her prey, before killing them, regardless of the gender. During their assault, she went after Dean and attempted to use her influence on Dean. Although it first appeared to affect him, Dean was able to break out of it and plunged her headfirst into a bath tub of holy water repeatedly. Bobby later exorcised her. Her host survived the possession.

Gluttony
He possessed a bald, skinny man who used mind control upon Isaac to make him consume drain cleaner at the sin bar. He was killed by Ruby's Knife at Isaac and Tamara's home when he, Pride and Greed ganged up on Sam.

Sloth
He possessed an overweight man and killed a Nebraskan family by making them too lazy to reach the stocked fridge in their home only a few feet away from where they were seated.

He was exorcised successfully by Bobby Singer after being entrapped in a Devil's Trap.

The vessel he possessed survived the exorcism.

Wrath
Wrath possessed a bald, pierced and tattooed man. At the sin bar, he remarked that he did not like hunters being in his place, in reference to Isaac and Tamara. He prevented Issac from attacking Envy.

He later possessed Isaac's dead body and used it to taunt the already devastated and vengeful Tamara into breaking their defenses. He was impaled with Palo Santo and exorcised by Bobby.

Its unclear if his first vessel survived his possession as he wasn't seen again.

Greed
She took the body of tall skinny brunette female, who appeared at the sin bar and was dowsed with moderate quantities of holy water by Sam, Dean and Bobby to save Tamara. She attacked the hunters with Wrath, Gluttony, Pride, Lust and Sloth and joined Pride and Gluttony in the pursuit of Sam Winchester.

She was killed by Ruby, who stabbed her chest using the demon-killing knife.

Pride
Claimed to be the root of all sin, possibly because it was Lucifer's pride that caused him to try to be better than God. As such he was implied to be their leader, leading Gluttony and Greed on their attack on Sam. He also mostly did the talking, and his companions obeyed his oders like stopping when Pride detected a devil's trap.

He engaged in conversation with Sam and mocked the hunter as a poor choice of Azazel as the chosen one. True to his nature as being extremely arrogant and prideful, he stated his refusal to acknowledge Sam as his leader.

He immediately sensed the presence of a devil trap in the upstairs spare bedroom using immense telekinetic strength to break the trap.

He appeared in a vessel as a tall, suited lawyer with curly brown hair.

He was killed by Ruby last following Gluttony and Greed using the demon-killing knife, piercing through his jaw and straight up his skull.

Powers and Abilities
Despite being black-eyed demons, as the physical embodiments of the seven deadly sins, they were quite powerful demons. As they approached, their presence caused lights to flicker, electronic devices to malfunction and even certain objects (such as trash cans) to vibrate. Its unknown how high the Sins ranked in the hierarchy of Hell but it is confirmed that they are subservient to Azazel in strength, rank or both.
 * Mind Control - Demonstrated by some of them, each demon can influence a person to do the sin that they represent, although they have to make physical contact to infect the person. Sloth made a family sit on a couch and die of starvation and dehydration, Gluttony made Isaac drink drain cleaner, Envy made a woman kill another one over a pair of shoes, Lust was able to make Dean passionately kiss her.
 * Possession - Like all demons, they could take control of a person's mind and body. Its implied they took hosts, who were guilty of each sin.
 * Telepathy - Envy had extensive knowledge of Tamara's history despite having no interaction with her before and without possessing her or Issac.
 * Terrakinesis - The Seven Deadly Sins possessed the rare demonic power to create tremors. Pride demonstrated this by creating a small earthquake to destroy a devil's trap on the ceiling on the floor Sam was on before attempting to kill him.
 * Telekinesis - Pride was able to telekinetically throw a door off its hinges.
 * Super Strength - Like all demons, they were very strong and could withstand almost anything. They were also noticeably stronger than average black eyed demons, as Pride was able to casually overpower both Sam and Ruby, another black-eyed demon though Ruby was able to casually kill Gluttony and Greed with her knife.
 * Invulnerability - They were invulnerable to almost all weapons, except for Ruby's knife and the Colt. They did possess demonic weaknesses such as holy water, salt and palo santo.
 * Immunity  - The sins possessed resilence to holy water. Although Holy water still affected them, and caused them a lot of pain, it took a significant amount to incapacitate them.
 * Immortality - They could potentially live forever; they were all at least five hundred years old when they encountered Sam and Dean.
 * Superhuman Knowledge - All of them possessed great knowledge,  such as about the sin they each represent and how it afflicted others.

Trivia

 * Interestingly, each of the four protagonists in "The Magnificent Seven" confronts the deadly sin for which they are most culpable. Tamara confronts Wrath, Dean confronts Lust, Bobby confronts Sloth and Sam confronts Pride.