Now well into its fifteenth season, Grey's Anatomy recently earned the title of the longest-running medical drama in television history.

The series has certainly developed its share of some of the most iconic characters in existence. Of course, with that, the show has also produced some of the most memorable losses. Grey's is loved for its diverse cast of characters, and the fact that their journeys always resonate with audiences.

The deceased of Grey's are too many to count, but here are five of those everyone probably misses the most, and five that no one ever really cared about in the first place.

ADELE WEBBER - SAD

ADELE RICHARD GREYS

Adele was iconic, but she was often overlooked due to her usually rare appearances. She emerged sporadically over the course of her nine seasons in Grey's Anatomy. Despite the small amount of screen time she received, actress Loretta Devine breathed so much life into this character.

Adele's scenes were most always memorable ones. She had been through her share of hardship by the time of her death, including a harrowing battle with Alzheimer's. At Dr. Bailey's wedding, Richard revealed to Meredith that Adele had passed away, and viewers' hearts broke. Even though Richard is now remarried to Catherine Avery, it's very hard not to miss the beloved Adele.

CHARLES PERCY - GLAD

There seemed to be no end to Charles Percy's irritating antics until he died in season six. When he and the other Mercy West residents transferred to Seattle Grace in the merger, Charles was portrayed as arrogant, and was quite hard to like as a result.

His death happened in the infamous hospital shooting. It's sad to say that this resident's only redeeming qualities surfaced then, making his final moments as he died in Dr. Bailey's arms, touching, memorable, and even a little bit tearjerking. But his character has probably long-since faded from most fans' minds at this point in time.

ELLIS GREY - SAD

Ellis Grey on Grey's Anatomy

What would Grey's Anatomy be without the original Dr. Grey herself? Ellis was a highly revered surgeon, whose life revolved around her work. When she was first introduced in the pilot episode of Grey's, she was ailing with Alzheimer's disease and living in a long-term care home.

Sure, she was often cold toward most people, but Ellis Grey was iconic in every way. It's sad Meredith never got to properly mend fences with her when Ellis was alive, and Maggie never got the chance to meet her birth mother. Though Ellis Grey's legacy lives on through many aspects of the series, it's hard not to miss her actual presence on the show.

7. HEATHER BROOKS - GLAD

Initially, every batch of interns is annoying. For Heather Brooks' group, character development never really took off. By viewers, they were mostly regarded as an inconvenience, since Grey's writers dedicated excessive amounts of screen time to them, when no one really cared.

With the exception of Jo Wilson, these interns disappeared from the show. Brooks was the only intern in her group that received an onscreen departure. While her death was (literally) a shock, it did not do much to resonate with the audience, as Heather, like her fellow interns, was underdeveloped. Similar to Charles Percy, Heather's death is probably the only thing viewers truly remember about her character.

GEORGE O'MALLEY - SAD

007, Bambi, Puppy, Heart in the Elevator Guy... whatever you want to call him, George O'Malley captured hearts from the very start of the series. The audience had been through a lot with George, loving him through even his most questionable decisions, because it was simply hard not to love him.

T.R. Knight portrayed an endearing character, one of the most memorable in Grey's history. In the end, after putting in five seasons to the series, George's fate was tragic. After being hit by a bus, he was regarded (for the better part of the episode) as a fatally injured, unidentifiable John Doe. Many would consider this an unceremonious end to a beautiful character.  The writers later attempted to redeem themselves with a touching scene in which Izzie nearly dies and sees George waiting for her in a presumable elevator to the afterlife.

REED ADAMSON - GLAD

REED GREY'S ANATOMY

Along with Charles Percy, Jackson, and April, Reed was a member of the Mercy West gang. Yet another victim of the hospital shooting, her death was indeed jarring.  It was perhaps the most intriguing moment in the history of her short-lived character.

Reed was conceited, and the fact that she attempted to strike up a flirtation with Alex shortly after Izzie's departure from the show fuelled fans' distaste for her. She was only in the show for a short time after being fired by Richard and later rehired by Derek. Reed was never really redeemed before she died, and though fans will always remember April slipping in a pool of her friend's blood, many are hard-pressed to remember Reed as a character.

LEXIE GREY - SAD

Chyler Leigh as Dr Lexie Grey in Grey's Anatomy

Lexie, to this day, is still one of the most mourned Grey's losses. So much so that the writers deemed it necessary to bring in Amelia Shepherd and Maggie Pierce, in Lexie's absence.

Though Meredith's dynamic with her "new" sisters is fun to watch and often endearing, these two have never quite filled the void that Lexie Grey left behind. She was the original Grey sister, and viewers watched the tumultuous relationship between her and Meredith grow into a loving bond. This worked to make Lexie's already gut-wrenching death, one of the most heartbreaking in the series.

DEREK SHEPHERD - GLAD

Patrick Dempsey as Dr Derek Shepherd Greys Anatomy

McDreamy's death was undeniably heartbreaking, and it was brutal to watch Meredith take him off life support. However, the on-again-off-again nature of the "Mer-Der" relationship, Derek's frequent mood swings, and the fact that he seemed to flirt with infidelity, provided McDreamy with his share of less-than-dreamy moments. After eleven seasons of this, it begs the question: is he really that missed?

Patrick Dempsey's natural charm gave Derek a one-of-a-kind quality, which made him absolutely unforgettable. But some might go as far to say that Meredith benefitted from Derek's death, after which she advanced her surgical career and won a Harper Avery award in the process.

MARK SLOAN - SAD

McSteamy was arguably even more iconic than his best friend, McDreamy. Mark Sloan was pompous, arrogant, and undoubtedly one of the most beloved characters in Grey's history.

His bromance with Derek was a fan-favorite. His friendship with Callie was adorable. His role in the Callie-Arizona-Sofia family was even more adorable. His relationship with Lexie was captivating and is still regarded to this day as one of the best Grey's romances. When Mark was introduced to the series, he was known as Derek's immature best-friend-turned-enemy. As seasons went on, McSteamy became a doting father, and highly regarded surgeon and mentor to several fellow doctors, including Jackson Avery, who followed in his footsteps.

By the time he was killed off in the ninth season, Mark Sloan was one of the most lovable characters on the show, and he is still missed by many to this day.

 NATHAN RIGGS - GLAD

Nathan Riggs during his time in the Middle East before he began working at Grey Sloan Memorial in Grey's Anatomy

Though he did not actually die, the memory of Nathan Riggs is burned into viewers' memories, and not necessarily in a good way. After a few seasons with this tiresome character and his short but contrived romance with Meredith, he finally left in a slightly ridiculous and poorly written arc.

Nathan appeared to be interesting at first, with his mysterious connection to Owen Hunt. But it wasn't long before the intrigue that once surrounded Dr. Riggs dissipated. His relationship with Meredith ended dramatically when he discovered that his dead fiancee, Megan Hunt, was actually alive, and well, that was that.

Nathan left Grey Sloan Memorial in the fourteenth season, but not before viewers were treated to a far-fetched episode packed with cringeworthy dialogue that primarily focused on his and Megan's move to Malibu. It was a relief for several to finally say goodbye to Nathan Riggs and the arcs that were put to rest with him.

NEXT: GREY'S ANATOMY: 14 PATIENTS EVERY TRUE FAN WILL REMEMBER (AND 6 WE'D RATHER FORGET)