Barney is mostly known for his quick one-liners and for being a womanizing ladies' man on How I Met Your Mother, but his character had more to him than just the tailored suits and pick-up lines. Barney went through plenty of changes throughout the series, both good and bad.
A lot of Barney's character arcs surrounded his dating life since that was such an identifier of his character. By the end of the series, he seemed to actually want to commit to a relationship, his siblings and parents, and even his own daughter but he ended up ruining a lot of his relationships as well.
Best: Wanting Commitment
Even though Barney and Robin's relationship was a bit out of nowhere on the show it was still a good character arc for Barney to actually want to commit to one relationship.
For most of the show, Barney was a player that liked to prey on women at bars and his bachelor life was an ongoing joke on the show, but it showed real growth when he wanted to marry and commit to Robin. It seemed like these two might actually make it after the show spent a few seasons building their relationship and eventual wedding.
Worst: Divorcing Robin
The show took time building up Barney and Robin's relationship only to say that the two were divorced shortly after getting married and Robin ended up with Ted by the end of the show.
This was an odd choice for Barney's arc as it seemed like he was growing and wanting to finally commit, but all of that growth was destroyed when he and Robin were divorced and he went back to his bachelor lifestyle.
Best: Becoming A Father
Although the show doesn't really show Barney as a father as it saves this reveal for the season finale final episode, there is still an emotional moment between Barney and his daughter acted with dramatic weight from Neil Patrick Harris.
Barney and Robin's divorce negated a lot of his character arc about finally wanting to commit, but some of that arc was saved when Barney had this moment where he commits to his daughter.
Worst: Obsessing About His Parents
Although it was nice that Barney was always there for his mother and repaired his relationship with his father, it was still odd that he was so obsessed with his parents and even tried to get them to reconnect at his and Robin's wedding.
It's meant to be comedic that Barney, and even his half-brother James, would be so obsessed with their parents' love lives, but it's just an odd, constant arc for Barney.
Best: Asking Ted Before He Proposed To Robin
This again shows that Barney does care and empathize with his friends even though in most of his storyline he has been a callous womanizer. Barney was planning to propose and fully commit to Robin, but he decided that he should first ask one of his best friends Ted, who has previously had a serious relationship with Robin if he was comfortable with Barney proposing.
It was nice to see that Barney does truly care about others and how his actions affect others and not only cares about himself.
Worst: His Relationship With Quinn
Barney began a relationship with Quinn after meeting her while she was working as an exotic dancer and Barney fetishized the relationship most of the time. He had even tried to propose to her although it never seemed like a very serious relationship and the two broke up before actually getting married.
Quinn seemed to be doing fine after the break-up and appeared in an episode to mess with Barney on his bachelor's night before marrying Robin, and Barney acts terribly by only talking about her stripping for him instead of treating her as his ex-fiance.
Best: P.L.E.A.S.E
Barney was always dismissive when someone asked him about his job on the show, usually responding with please, but it was revealed that he was actually answering truthfully, and please was an acronym for his job.
He revealed that he was the guy who signed any type of documents that might include illegal activities at his law firm, but then also revealed he had been working with the FBI as an informant against his corrupt firm.
Worst: Writing The Bro Code
Barney wrote the bro code in the show, and another version was published for fans to buy, and it was basically full of scams he had done to try to get women.
Barney was a womanizer throughout most of the series and this book was the ultimate demonstration and collection of all of his scams that he referred to frequently throughout the show. Even though Barney changed a lot throughout the series, his womanizer status was pretty steady and this book proved it.
Best: Reconnecting With His Father
Though Barney was a little too obsessed with his parents' life, it was still a nice change to see Barney reconnect with his father and forgive him for acting as his uncle when he was growing up.
The fact that Barney was willing to mend his relationship with his father shows a maturity to the character that has grown throughout the series.
Worst: Still A Womanizer
Although Barney goes back and forth and begins to show that he does care about the women he has relationships with in later seasons, it's still pretty clear that he remains a womanizer overall.
The show tried to bring some depth to the character, but the show often fell back into Barney making jokes about women and dating that seemed to negate any real character arc he could have had by the end of the series.