When we meet Dean in season 1, he is steadfast and loyal to his father, John. Sam even considers Dean to be John's loyal soldier. We find out that Dean wasn't allowed much of a childhood by John, causing him to grow up faster than Sam. In some ways, he acted more like a parent to Sam than John did. Still, Dean idolized John. Also, following John's orders meant staying alive.
Later, Dean both loves and questions John. Exposed to the hunter life sooner than Sam, he believes in the mission, and he is good at it. Yet, Dean also questions it and his role. In the last seasons, we see Dean becoming more and more like John. Still there are ways that he is incredibly different than John. Read on to find out.
Like John: Is Judgmental and Harsh
While this is nothing new to Dean, he is more judgmental and harsh in Season 14 and 15 than he had been before. We see this mainly in his treatment of Castiel. Since Castiel kept Jack's situation (nearly soul-less state) to himself, Dean blames Castiel for all that follows. Additionally, he has less respect for Castiel. When Castiel decides to leave the Winchesters, Dean doesn't seem to care and definitely doesn't stop him. Sam calls to try to get Castiel to come back, but Dean doesn't call once.
John was a very judgmental and harsh person. Even with those he cared about (Dean and Sam), he seemed to measure them against a standard they never could meet.
Not Like John: Has Self-Doubt and Doubt in the Mission
Season 15 seems to be a nearly impossible situation: Chuck/God is determined that the world will end with the brothers killing each other. He wants to pit brother against brother, and since Chuck/God makes the rules for this world, their own free will seems futile. Likewise, Dean wonders about his identity and mission. How much did Chuck/God craft of his personality and journey, and how much of it was really him?
In this case, Sam is more like John, as John doesn't possess a lot of self-doubt. John believes in the mission, almost fanatically so. While it's true that John never had to deal with Chuck/God or the astral sphere like Sam and Dean, he also never doubted his mission, although Sam and Dean may have had a healthier childhood had he done so.
Like John: Commitment to the Hunter Life
Although Dean does have doubts about his life as a hunter, he still values it. In Season 15, he needed to be reminded of its importance. When he met up with an old hunter friend whom his father had once admired and was no longer living the hunter life, Dean was intrigued and may have felt tempted. Then he found out that the hunter got his great life by not just abandoning the hunter life, but also abandoning the hunter principles of protecting innocents. This was the road trip that Dean needed to get him back on track. Because when push comes to pull, Dean values doing the right thing and protecting people. He just needed to be reminded.
John started up this family business of hunting monsters and protecting people. He taught both Sam and Dean to do the same. It is one of John's values that Dean (especially) cares about. Perhaps having a little doubt helped Dean to feel even more committed to this cause. He isn't just blindly following his father's orders, but rather choosing this life.
Not Like John: Better Father, Capable of Greater Empathy
When Jack was born, Dean doubted that Jack was good. Jack actually was scared of Dean and really wanted his approval. Kelly Kline left her son in good hands as he had three fathers: Castiel, Sam, and Dean. Shortly, Dean warmed to his role as a father figure to Jack.
In Season 14, it looks like he had John's determination to sacrifice his own son for the public good, echoing John's previous directions to Dean concerning Sam. Earlier, John feared that Sam would go dark and made Dean promise to kill Sam if needed. Luckily, Dean stops himself from killing Jack, realizing that he loves Jack and would do anything for him. Although John could be a good dad, in the end, he would've killed Sam, thinking of it as a sacrifice and a great mercy.
Like John: Demands All or Nothing Loyalty
John demanded extreme loyalty of his sons, something that didn't always make Sam comfortable. Eventually, the two do question John, but it took a while for Dean to get there.
Dean may be more nuanced in his aptitude to see the complexity of the situations than John was, but he still demands all or nothing loyalty. That said, if you are loyal to Dean, he will do a lot to help you out, too.
Not Like John: Stronger Sense of Humor
John may have had a sense of humor once, but due to his hard life, he is mostly serious. Dean also deals with a very hard life, yet he's kept his sense of humor. At times, his sense of humor is gallows humor and at other times, he has a silly sense of humor. No doubt, his sense of humor has gotten him through difficult times.
Additionally, Dean still takes almost childlike joy in specific things like the Wild West and Scooby-Doo. His sense of humor and joy helps him appreciate the moment and cope with the challenges as they come.
Like John: Is Extremely Devoted to Mary
John began to have a hunter life when Mary was tragically killed by a demon. His whole mission centered around getting revenge for her death. Due to this, both Sam and Dean grew up to be hunters.
When Mary is killed in Season 14, Dean is torn apart. His anger sees no nuance, and poor Castiel suffers for it since he hid Jack's condition from Dean.
Not Like John: Respects and Listens to Sam
Initially, Dean treated Sam like his kid brother, only listening to him part of the time and barking orders at him. However, these two have been through a lot, and Dean respects Sam, listening to him. When Dean is in one of his moods, Sam is really the only one that can convince him to look more deeply into the situation.
John loved Sam, but didn't always listen and value him the same way. Dean and Sam are equal partners in their family's mission.
Like John: Commands Those Around Him
Granted, Dean often knows what to do, and by commanding those around him, he makes effective plans. However, sometimes, he doesn't listen to others. Although Dean doesn't keep people in the dark like John did, Dean still commanded them, expecting loyalty. He even does this with angels and demons, beings that have considerably more power than he does.
Sometimes this habit is helpful, and other times it isn't. Luckily, Sam does call him out when he needs a good reality check.
Not Like John: People Want to Be His Friend
It's not that John didn't have friends, but John had a habit of flying solo and burning bridges with people. Even Bobby wasn't talking to John due to being angry at him. John was respected, but he wasn't always befriended or desired as a friend.
In contrast, everyone wants to be Dean's friend from Crowley to Castiel. People and supernatural beings feel bonded with Dean in ways that they never did with John.