Even with Supernatural being a dark fantasy series, the show placed heavy emphasis on character quality. Dean Winchester was one of the two leads alongside his brother Sam, although Dean had arguably the more tragic arc. This was due to Dean's selfless love for his brother that saw him sacrifice his own life and happiness to ensure that Sam remained safe.
A look at Dean Winchester's timeline gives the best view into how tragic his life was, along with the events that led to the conclusion of his arc. Since the Supernatural timeline is told out of order due to Dean's experiences with time travel, his story takes shape before he was even born.
1861: Dean Retrieves Phoenix Ashes From The Old West
In 1861, Dean chronologically first appears on Earth when he's sent from 2011 to the past in Sunrise, WY. He arrives with the intention of hunting down a Phoenix, whose ashes he requires to slay the monster Eve in the future. Dean tracks down the Phoenix, a man named Elias Finch, and challenges him to a duel. Dean's brother Sam Winchester arrives with a gun that can slay almost anything in the world known as the Colt, which Dean uses to off Finch and turn him into ash.
However, before Dean can collect the ashes, he's pulled forward in time and vanishes from 1861.
1943: Dean Retrieves The Hand Of God From The Doomed USS 'Bluefin'
In January 1943, Dean resurfaces in the Atlantic Ocean during World War II - having traveled from 2016 - on the USS Bluefin, a submarine carrying an artifact that is actually a Hand of God - an item that has the power of God sealed within it. Dean realizes the crew is attempting to fight off German destroyers and aids them, but impresses upon their leader Delphine Seydoux, who is part of the Men of Letters faction, that he needs the Hand of God.
However, the Germans are able to overwhelm the Bluefin, forcing Delphine to use the Hand of God to obliterate them and her own crew. Right before this happens, the archangel Lucifer appears to save Dean by taking him back to the future.
1944: Dean Teams Up With Eliot Ness
On November 4, 1944, Dean zaps into Chicago, IL, traveling from 2012. Having been caught up in a scuffle with a man called Ethan Snyder, Dean learns Snyder is actually Chronos, the god of time, who was draining the life forces of people from the future to travel to 1944 where he's in love with a woman named Lila Taylor. Dean ends up coming across Eliot Ness, who turns out to be a hunter of the supernatural like him.
By November 5, 1944, the two manage to track down Lila and expose Chronos's truth, following which Chronos assaults Dean. Eliot throws Dean the wooden stake that can slay Chronos before both of them vanish into the future.
1973: Dean Meets His Parents, John Winchester & Mary Campbell
On April 30, 1973, Dean shows up in Lawrence, KS, having traveled from 2008. Dean comes across his father, John Winchester, who is 29 years old at the time. Dean follows John to see him meeting his girlfriend Mary Campbell, who Dean is aware will be his mother. He's also shocked to learn his mother is a hunter while his father hasn't become one yet, and convinces Mary's father, Samuel, that he's a hunter as well, after which he makes acquaintance with the Campbell family.
By May 2, 1973, Dean learns the demon Azazel is hunting the Campbells and reveals to Samuel who he is, only to find out Azazel is possessing Samuel. Azazel learns of what is to come in the future and has been ensuring that John and Mary end up married so they can have a child that Azazel wants to corrupt. Azazel slays both of Mary's parents along with John and forces her to make a deal with him to grant him permission to enter Mary's house in 10 years. After she agrees, John is brought back to life while Dean is pulled back to the future.