Now in its fifteenth season, fans have seen characters change and grow in the Supernatural series. While the main focus of the series is the Winchesters brothers, other characters also have evolved, and one of those characters is Castiel. Initially, Castiel was a devoted angel sent by God to pull Dean from hell. He developed strong connections with the Winchesters, but more so with Dean.
As powerful and intriguing of a character that this angel is, there are times he was overrated as well as times he was underrated as a character on Supernatural.
Overrated: His Angel Powers
When Castiel enters the scene, he is extremely powerful. He pulled Dean from hell, something not many can do. In trying to merely talk to Dean, he caused radios and televisions to blow up. When Pamela tried to see his face, one glimpse blinded her. Demons were terrified of him, and Castiel seemed like he could heal anyone.
Later, in the series, his powers are taken away, then they come back, but were somehow limited. He has limited capacity to heal people, and his powers no longer strike fear in demons.
Underrated: His Role as a Father to Jack
Jack has three fathers: Castiel, Dean, and Sam. When Jack's mother (Kelly Kline) was pregnant with Jack, she wanted Castiel to protect her son and serve as the father figure. By having such an angelic role model, Jack would be a better person even though he was Lucifer's son. It worked, and Castiel, along with Dean and Sam, became fathers and role models.
On top of this, Castiel loves Jack. This is shown when Dean thinks that soul-less Jack needs to be killed, Castiel stands in the way, trying to protect his only son.
Overrated: His Authority
When Castiel first comes into the series, he tells Dean that Dean should respect him. No doubt, in the beginning, Castiel seems to be an angel well-respected by other angels, and he is of high rank. Whether it's because of his mistakes with trying to become a god or following Metatron, his authority lessened.
At times, Dean seems to have more authority in their relationship. There are times where Dean is not only disrespectful but brutal in his judgment of Castiel. Truly, Dean should show him more respect.
Underrated: His Fighting Ability
Castiel is a fighter. In season four, Castiel is juggling his job with Dean and a battle in heaven. Dean tells him that he thought angels were guardians with fluffy halos, to which Castiel responds, "read the Bible. Angels are warriors of God. I'm a soldier." From the way that the other angels regard Castiel in earlier seasons, it's clear that Castiel was a good soldier—one of the best, really.
While fans have seen Castiel fight on Earth, it looks like there is more to Castiel's fighting ability than has been shown as of yet.
Overrated: His Trustworthiness and Righteousness
In season 15, Castiel is trustworthy and righteous. He actually has a better perspective than Sam and Dean, once even calling Dean out. However, the consistency of his trustworthiness and righteousness can be called into question.
For instance, it was he who let loose the Leviathans, absorbing them and other souls/supernatural beings to get more power and become a god. He unleashed them because he felt like he knew what he was doing and that he would become a better god because of it. His judgment is called into question in other instances, as well. The Winchesters sometimes are disappointed in him, feeling that their trust was misled. However, they continue to give him more chances, and he becomes a more trustworthy and righteous individual. It's just not a consistent trait in the show.
Underrated: His Pizza Man
Castiel starts a quasi-relationship with Meg, the demon. Sweetly and ionately in a moment of danger, he kisses her, telling her, "I learned that from the pizza man." Meg replies, clearly pleasantly surprised, "well, a plus for you." Whether it was through watching porn or just getting in touch with his sexual side, Castiel seems to be both a good lover.
In a later season, he has sex with another angel that was possessing a human. While that particular angel wanted to kill him, she enjoyed being intimate with him. In an alternate future, fans learn that Castiel is human and fully in touch with his sexual side.
Overrated: His Rapport with Heaven
At one point, Castiel is very respected in heaven. They want to follow him. Even when he's on the outside and out of approval, there are angels who still believe in Castiel. However, his rapport with heaven is inconsistent. The longer he stays on Earth, the less he seems to have in connection with the angels.
His worldview becomes more nuanced than theirs overtime, and he can't really count on a rapport with them anymore. He has chosen his own side or the Winchesters' side over heaven many times. His rapport with heaven is dicey, at best.
Underrated: His Ability to Adapt
The Castiel fans witness in season 15 is very different than the Castiel that they were first introduced to. Castiel has evolved. He has learned from his mistakes, and he has adapted to this world. For a time, he had to live as a human, and, during that time, he learned the beauty of humanity. When he was an angel, he considered humans as meager as ants. Now, he is willing to fight for them.
His ability to adapt is also shown in his intelligence. For instance, when the angels are looking for him, Castiel evades them for a while by flashing in and out of a chain restaurant. Since each restaurant in each location looks exactly the same, it's hard to locate him. He successfully knows, understands, and uses his surroundings for protection.
Overrated: His Decision-Making Skills
While Castiel has gotten better with making decisions, he made several weak decisions over his time in the series. He tried to become a god, consuming and then freeing the Leviathans. He followed and believed Metatron, a grand betrayer. Thinking he was making a good decision, he even allowed Lucifer to possess him and his vessel. For an ancient being, Castiel has seemed fairly naive. Of course, he's gotten better in later seasons—it just took him a while to get there.
Underrated: His Devotion to the Winchesters, Especially Dean
Castiel is family to the Winchesters. He protects them and is even willing to sacrifice himself for them. While he is close to both, he shares a special bond with Dean.
In season six, Sam had been praying to Castiel and didn't hear anything back. Dean prays to him once, and he comes. When Sam is upset, asking if Castiel likes Dean better, he responds, "Dean and I do share a more profound bond. I wasn't going to mention it."