Supernatural is a TV show that began in 2005 on the network known as The WB. The show's life was in the balance when the network merged with the CW network and became The CW. After two successful seasons on the air and a huge fan base developed, the creator Eric Kripke launched the first comic series, a prequel to the show titled Supernatural: Origins.
Dean Winchester was born January 24, 1979 to John Winchester and Mary Campbell. He has a younger brother Sam, referred to as "Sammy" mostly by Dean. In the comic series, Dean first appears as a young child and then by issue #2 he's about ten years old. During this time Dean has not developed any of his weaponry or criminal skills but since the TV series shows us Dean in the future, those traits are part of his character since Mary's unusual death and as a result of John's child rearing skills.
When younger brother Sam was just six-months-old, a yellow-eyed demon entered the nursery of their Lawrence, Kansas home. While checking on baby Sammy, Mary interrupted whatever the YED was doing and was killed by the Yellow Eyed Demon (aka Azazel). From that point, the Winchester men's lives were never normal.
John, certain that the boys (especially Sammy) are not safe, takes them across the country to learn from people about magic and demon-hunting.(Season 1:1 - Pilot)
These events are the culmination of a decades long plan of Azazel's (Season 2:21 - All Hell Breaks Loose Part 1). Several years prior he made deals with several young men and women, he would save the life of a loved one in exchange they would allow him entry into their homes in ten years time. Mary Campbell, a demon-hunter and the daughter of demon hunters, made one such deal to save the life of a young solder, recently returned from Vietnam, who was her then boyfriend and future husband, John Winchester. (Season 4:3 - In The Beginning)
Dean learns his weapon skills from his father John who is a former US Marine though we learn that Dean's innate ability as a hunter is inherited from his grandparents Samuel and Deanna Campbell and his mother Mary Campbell Winchester. (Season 4:3 - In The Beginning) Dean takes his role as big brother very seriously and watches over Sam at all times. He develops excellent aim and knowledge of man-made weaponry but mostly relies on hand-to-hand combat and his favorite shotgun in battle. The traits listed in Dean's profile are ones that are certain to develop as his matures in the comic book.
One area that's a bit different from the TV show to the comic is when John leaves the boys in a motel room. In the show, he leaves Dean with a shotgun and orders him to protect Sam; in the comic, the boys are left with the front desk clerk. It's not known by issue #2 when Dean's lessons with weapons and will begin. In the show we also know that Sam and Dean were taught credit card scams in order to fund their demon-hunting. They also have a long string of aliases by the time they are in their 20's.
When John goes missing Dean reunites with his brother Sam to investigate, during the course of this hunt, Azazel murders Jessica, Sam's girlfriend, in the same manner as Mary. It is later revealed by Azazel that this was to push Sam back on course to become the leader of Azazel's demon army. (Season 2:21 - All Hell Breaks Loose Part 1 and Part 2).
Dean and Sam eventually reunite with their father who has been hunting for The Colt (Season 1:20 - Dead Man's Blood). Made by Samuel Colt, consecrated and blessed by several different beliefs, it is the ultimate weapon as it can kill any demon. It is also the mystical key to an enormous Devil's Trap that Samuel Colt created in Wyoming to contain a gate to Hell. (Season 2:21 - All Hell Breaks Loose Part 2)
After John is kidnapped by Meg Masters aka Azazel's daughter, Sam and Dean find and free him and escape to a secluded safe house in the woods (Season 1: 21 - Salvation), however during the course of the night Dean realizes that Azazel has possessed their father. Azazel then proceeds to torture Dean and taunt Sam while in John's body. It is only the sight of Dean dying that gives John the strength to push past Azazel and regain control of his body. While this respite is temporary it allows Sam enough time to grab The Colt and shoot John, forcing Azazel from John's body. All three Winchester's escape and as Sam drives them to the hospital they are blindsided by a semi being driven by a possessed driver. (Season 1:22 - Devil's Trap)
Sam and John survive the accident relatively unscathed, however Dean, who had suffered massive internal injuries before the crash due to Azazel's torture, remains comatose. While in the coma, Dean's spirit makes friends with a young woman named Tessa, also in vegetative state. Together they try and figure out how to deal with their situation with Tessa strongly suggesting they let go while Dean attempts to get them back in their respective bodies. It turns out that Tessa is actually Death, (inspired by Neil Gaiman's Sandman series), and has come to guide Dean to the afterlife. However Tessa is thwarted by Azazel when he jumps into her body and forces her to restore Dean to life. This is a result of a deal that John Winchester makes: his life, his soul and The Colt, in exchange for Dean's life. (Season 2:1 - In My Time of Dying)
When Dean wakes he remembers nothing of his encounter with Tessa but feels as if something is very, very wrong. John comes to tell Dean how proud he is of him and how much he admires and loves him, and then leaves to get coffee, in actuality he goes to Azazel to live up to his end of the bargain, and dies, devastating Dean and Sam. (Season 2:1 - In My Time of Dying)
Dean and Sam continue to hunt, but the death of their father leads them both, particularly Dean down a self destructive path. This is due to John's final words to Dean that give him a task he thinks he is incapable of doing. Finally after months of Dean deliberately trying to get killed does Sam confront him and learns that John's final words to Dean were that Sam would have to be killed if he began to give into the inherent taint of Azazel's blood. (Season 2:10 - Hunted)
John wasn't the only one who felt that Sam would have to die, another hunter, Gordon Walker, begins tracking the Winchesters and the other Special Children, killing them off one by one. (Season 2:10 - Hunted) Gordon tries several times to convince Dean to turn on his brother to no avail and eventually gathers other hunters to help him in his quest to kill Sam. (Season 3:2 - The Kids Are Alright) When Gordon is bitten by a vampire, his hunting specialty, and turned he becomes near unstoppable, killing other hunters in his quest to destroy Sam. He traps the Winchesters, separates them and attempts to vamp Dean, before being decapitated by Sam (Season 3:7 - Fresh Blood)
Gordon, it turns out, is only one of several groups tracking the Winchesters as Special Agent Victor Henriksen of the FBI, starts hunting the brothers, whose activities to the outside world look to be the work of serial killers. (Season 2:12 - Nightshifter/Season 2:19 Folsom Prison Blues) After being possessed and subsequently exorcised by Sam and Dean, Victor becomes an ally, going so far as to fake their deaths both physically and in the FBI's database. Unfortunately Victor is murdered by Lilith the Deciever, a higher level demon who appears to wants Sam dead and Dean's soul. (Season 3:12 - Jus In Bello), it is later revealed that Lilith, Azazel and Ruby are working together to destroy the bond between Dean and Sam so that Sam will open the final seal and become Lucifer's vessel. (Season 4:22 - Lucifer Rising)
When Sam is kidnapped by Azazel, along with several other Special Children, and placed in a demonic showdown, Dean stops at nothing to find his brother, which he does, just in time to see him stabbed by the only other survivor of Azazel's weeding process. Sam dies in Dean's arms, destroying what's left of Dean's sanity. In desperation Dean goes to a Crossroads Demon and makes a deal, continuing the vicious cycle that started with Mary, his life and soul for Sam's. The Crossroads Demon takes the deal and gives Dean one year to live. Sam returns from death, initially unaware of Dean's deal, and together with their allies Bobby Singer and Ellen Harvelle they set about stopping Azazel from opening the Hell Gate with The Colt, with Dean being the one to shoot him with The Colt, destroying him forever, but not before Azazel is able to plant a seed of doubt in Dean's mind that the brother he brought back is 100% Sam. (Season 2:22 - All Hell Breaks Loose Part 2)
The following year Sam looks for every way possible to save Dean from his deal up to and including allying with the demon Ruby, who states that she is one of many demons who are still ready and willing to follow him, and going behind Dean's back and using his demonic powers. All of this is in vain as Ruby has lied to Sam about her ability to save Dean from his deal and was using the opportunity to push Sam to become the demonic warrior that Azazel wanted him to be. Dean dies on May 15, 2008 ripped to shreds right in front of Sam by Lilith's hell hounds and sent to hell to be tortured in turns by Lilith and Alistair. (Season 3:16 - No Rest For The Wicked)
Dean spends 40 years in hell, 4 months in earth time, being tortured by Alistair, who wants Dean to join him and become his disciple, Dean resists for 30 years, however after the 30th year Dean gives in, and much to Alistair's delight becomes a torturer. This, more then his own torture, is Dean's worst memory of hell. (Season 4: 11 - Family Remains).
Dean is rescued from hell by the angel, Castiel, who is commanded by God to pull Dean out. Dean resurrects in his own coffin on September 18, 2008. At first panicked, as he has no idea where he is or how he got there, Dean claws his way out of his coffin. Once above ground he sees that the area surrounding his grave site for miles has been utterly destroyed. Dean makes his way to an abandoned gas station where he finds food and water. He also finds a newspaper that gives the date as September 18, 2008. He goes to clean the grave dirt off and realizes that all the marks and scars from his previous life are gone except for one: the protection against demonic possession tattoo that he and Sam had gotten (Supernatural 3:12 - Jus In Bello) and a large hand print on his right arm. As Dean tries to figure out what is going on a high pitched noise is heard, shattering every bit of glass in the gas station and causing Dean to collapse.
He makes a run for it, first trying to contact Bobby Singer, who hangs up on him, and finally hot wiring a nearby car. It is later revealed that it was Castiel trying to communicate with Dean, thinking that because Dean is special and chosen of God he would be able to withstand the sound of Castiel's true voice and form. (Supernatural 4:1 - Lazarus Rising)
Dean and Sam reunite but Sam continues to lie to his brother about his involvement with Ruby and the use of his demonic abilities, leading to a confrontation in which Dean starts to leave. (Season 4:4 - Metamorphsis) Dean is warned by Castiel that Sam is going down a dangerous path and if Sam doesn't stop of his own will then the angels will stop him. (Supernatural 4:3 - In The Beginning)
Castiel tells Dean that the angels have been ordered by God to follow Dean's orders when their assignments coincide with the Winchesters' cases. (Season 4:7 - It's The Great Pumpkin, Sam Winchester) This information, combined with the information given by Anna Milton, a young woman who can hear angels and see demons, that the day Dean was pulled from hell was the first day she heard the angels speaking and what they were saying were praises: 'Dean Winchester has been saved' (Season 4:9 - I Know What You Did Last Summer), has led to speculation that Dean is Heaven's Chosen, much as Sam was Azazel's Favorite.
Anna Milton, who is actually an angel who ripped out her own grace and fell to earth, falls in love with Dean as he, Sam and Ruby fight to protect her from both the demons, who want to use her ability to hear the angels speaking to plot against them, and the angels, particularly Uriel, who see her as an abomination. However Anna finds her grace and restores it to save Dean, Castiel, Sam and Ruby from Alistair and his demons, destroying her human form in the process. (Season 4:10 - Heaven and Hell)
Dean spent last year in a race against time as Lilith and Alistair were breaking 66 of the 600 Seals that hold Lucifer captive, which is the reason that the angels are walking the earth for the first time in 2000 years. He was also desperately trying to save Sam from himself as Sam continued to use his demonic abilities and becomes more and more embroiled in Ruby's plans. (Season 4:2 - Are You There God? It's Me, Dean Winchester).
It has been revealed that Dean himself is one of the 600 Seals holding Lucifer in hell ( Season 4:16 - All My Sins Remembered) and that when Dean finally broke under Alistair's torture in hell and agreed to torture other souls the first Seal (Dean) was broken: "And it is written: When a righteous man sheds blood in Hell the first seal shall be broken, as he breaks so too shall it break". Castiel reveals that because Dean was the first seal broken he is the only being in heaven, hell and on earth that can stop Lucifer. At first it was assumed Dean himself could stop Lucifer but it is later revealed that Dean is the human incarnation and vessel for the force that would stop Lucifer: the Archangel Michael.
Because both the Campbell and Winchester families are direct descendants of the Nephalim, the children of the angels who fell in love with humans and mated with them, as well as they birth order and personalities, Dean and Sam are the perfect genetic, physical and emotional vessels/hosts for Michael and Lucifer. Michael, in the form of a young John Winchester, reveals to Dean that every choice, every meeting, every happenstance the Campbell and Winchester families made over the course of centuries led to Dean and Sam being born in fulfillment of several prophecies (Season 5:12 - The Song Remains The Same) and it also comes to light that Mary and John's meeting and bloodlines were so important that the leading Cherubim (aka Cupid) was dispatched to insure that they met and fell in love (Season 5:13 - My Bloody Valentine).