The hit ABC medical drama Grey's Anatomy might revolve around Meredith Grey but it has given audiences some beloved characters over the years.
The peds surgeon, Alex Karev, played by Justin Chambers, was probably one of the few characters who grew the most during the course of the series. From being a callous jerk to a pillar of strength for Meredith throughout the many difficult times that she went through, to becoming one of the more mature people in her life, Alex saw quite a transformation in terms of growth. Yet, the abrupt departure of the actor in season 15 seemed to undo all the character evolution and send Alex back to the early seasons of the show.
Season 1 & 2: Arrogant & Self-centered
Alex Karev was introduced as an arrogant, self-centered brat who couldn't care less about anyone and didn't even make an effort to be civil to his colleagues. He was, in fact, a sort of foil to the softer, more gentle George O'Malley.
His not-a-care-in-the-world attitude was a major problem in the earliest seasons, causing Cristina Yang to coin the nickname 'evil spawn' for Alex.
Season 3 & 4: A Tad Mellow
Alex was still a bit of a jerk in season 3 and 4 but he had grown a tad less self-absorbed, thanks to Izzie's faith in him, and therefore a tad more mellow.
Alex also started getting attached to one of his patients, Ava, who was admitted after a horrific accident that had caused her to be completely disfigured. He grew to be fond of her, meaning that he was at least capable of thinking about others, and even made a relatively mature decision when he asked Ava to move on and be with her husband.
Season 5: Growing Up
Season 5 was significant for Alex as he became seriously attached to Izzie Stevens and was devastated when the latter was diagnosed with cancer.
Alex even went on to marry Izzie, knowing well that she was a terminal patient and would need the utmost care and love. It seemed as if the smart-mouth young surgical intern had found the anchor he was looking for in life, becoming accountable to someone else for the first time in his life.
Season 6: Coping With Life
Life had other plans for Karev and Izzie left him without so much as a word. It seemed like whatever strides Karev had taken as a person was about to go out the window.
Alex once again started falling back on his old ways in the aftermath of Izzie's departure. However, the season finale had a humbling moment for Alex Karev when he was shot by the gunman who later also tried to shoot and kill Derek Shepherd.
Season 7: Sliding Again
The shooting incident succeeded in making Alex rather more aware of his mortality. He initiated a project to offer treatment for African children who were not able to gain access to standard medical treatment.
Alex did, however, slide back to being the callous selfish guy he always had been from time to time and even told on Meredith when he thought he saw her attempting to tamper with the Alzheimer's clinical trial. He did realize his folly eventually but not before he had messed up Meredith's life.
Season 8 & 9: Mature Decisions
Season 8 saw Alex taking a bit more responsibility. He even put his patient's life first and arrived late for his viva exam that would determine his career henceforth.
Alex finally had some good news when he got offered the peds fellowship at John Hopkins Hospital, but following the devastating accident at the end of season 8, he made a mature choice and decided to postpone his fellowship to help run the peds department at Seattle Grace, now known as Grey Sloan Memorial. He also felt guilty for letting Arizona Robbins, with whom he had a mentor-mentee relationship, take his place in the plane that crashed on its way to Boise.
Season 10: A Few Good Things
Alex had a better spell both professionally and personally as he was offered a position in a high profile private organization where he could make a lot of money for the first time in his life. Of course, good things were far and few between in his life so he had to go mess it up eventually, but at least he got a taste of a life that he had never had the chance to savor.
Personally too, he finally seemed to move on from Izzie and commit to Jo Wilson, the young intern who joined Grey Sloan from season 9 onwards. More is also revealed about his past and his family, indicating that Alex has overcome many obstacles in his life to accomplish what he had.
Season 11 & 12: Conflicted
Gone was the arrogant young intern of the early years; Alex was now one of the best surgeons at Grey Sloan, with a much more genial personality in general. He also tried to be there for Meredith when the latter lost her husband in a shocking accident. In fact, Alex had now become Meredith's 'person', now that Cristina had left.
He did still have some of his bull in a china shop moments though, which was contrary to his otherwise mellowed nature--in the season 12 finale, he hit DeLuca under the impression that the latter was forcing himself on Jo. His actions came from a place of love and care but were rather reminiscent of the old Alex.
Season 13 & 14: Big Steps
Alex went on to make some important, mature decisions in seasons 13 and 14. He tracked down Jo's abusive husband and managed to keep his calm.
He also finally managed to get Jo to marry him, in a rather hilarious wedding. Before his final exit from the show, the now almost adorably goofy Alex was all set for a happier life.
Season 15 & 16: Stunted Evolution
Alex had evolved very much as a person by seasons 15 and 16; not only was he married, he had also got himself the position of Chief of Surgery at the Pacific Northwest Hospital, hoping to turn the hospital around.
However, the peculiar departure of actor Justin Chambers towards the end of season 16 somehow managed to take the character back several years, making him appear thoughtless and selfish. Sure, Izzie was his one true love but to leave his wife Jo without a word, and simply sending letters thereby not having to confront anybody in person, seemed like something the older, less mature Alex would have done. Though he had transformed significantly as a human being, he was at heart still the callous ol' Alex.