No one knows true heartbreak until they've watched several seasons of "Grey's Anatomy," especially in one sitting. In very "Game of Thrones" fashion, "Grey's Anatomy" doesn't allow you to have a favorite character -- whether it's a patient, an intern, a resident, or even the Chief of Surgery, no one is safe in "Grey's Anatomy." If you're lucky, your favorite character will disappear, and if not, they get hit by a bus or semi. Whether you've barely started the series, watched every season 20 times, or never watched a single episode, here are 11 of the best, or maybe worst, deaths to have occurred throughout the many seasons of "Grey's Anatomy."

11. Charles Percy

I’ll be the first to admit I hated Mercy Wester Percy -- so much that I’m wasn't even sure if Percy was his first name or last name. But dang did his death in the Season 5 shooting hurt Bailey, who did her best to save this coworker of hers, but in the end was thwarted by the elevators that were turned off to impede the gunman’s escape.

10. Doc

I may or may not have liked him better than Percy, and come on, how can you not be sad about the death of a dog, especially to something like cancer. Not to mention everything he symbolized in the middle of Meredith and Derek’s early relationship. Watching her cry at the death of her dog, and what she thought was the death of her relationship was tough to watch. I miss the early seasons when that was all we had to deal with.

9. Heather Brooks

Intern Brooks, a.k.a. “Mousey,” from Season 9, was taken before her time. She was weird and had social anxiety, but still, she was a good person and a good doctor. It was sad enough that her death was caused because of her concern for Doctor Webber’s safety above her own, but even more sad because it should have been Shane, a fact that both the audience and Shane know.

8. Dylan Young, a.k.a. Bomb Squad Guy

Ah, Season 2, we miss you. Things were so much less complicated back in Season 2. Dylan was only alive for two episodes, but his death hurt us because we thought everything was finally okay. After so much tension and Meredith "Death Wish" Grey shoving her hand into the body cavity, we thought we were in the clear, but as always, we were wrong.

7. Craig Thomas

He was the hero we didn’t know that we, along with Cristina, needed after the plane crash. He was her Mayo Meredith Grey -- her person to help her recover, her glue to help put her back together. He knew how she felt after the crash because he lived through it, and he showed her old techniques that were new to her. What we never saw coming was his abrupt death during the middle of a procedure. His death, unlike many, wasn’t traumatic or horrifying, but still, nonetheless sad.

6. Denny Duquette, Jr.

Denny’s death almost made me wish he had died when Izzie cut his LVAD wires. Watching him wait for Izzie and her never coming crushed me -- he died alone while she tried on dresses. Denny’s death hurt fans so much because, like Bomb Squad Dylan, it wasn’t supposed to happen. The problem was fixed, he had a new heart, he no longer needed to have the LVAD or stay in the hospital, and he got the girl -- by most accounts that should equal a happy ending. But Denny’s death proved that it wasn’t possible for everyone to have happy endings.

5. George O’Malley

We always remember our firsts -- and that’s why George’s death stays with us, even so many seasons later. George was the first time we realized that our favorites, our main characters, were not immune to the deaths that they worked so hard to prevent. He reminds us of the innocent days of "Grey’s Anatomy" -- back when it was just our favorite interns: Karev, Izzie, Meredith, George, and Christina doing their best to become the best surgeons they could be. Now, with only Karev and Meredith left from their class, we wish we could go back to those days.

4. Henry Burton

Denny 2.0. We thought Shonda Rhimes couldn’t possible do this to us again, but we were wrong. Teddy, hung up on Owen for so long, finally found love in patient-turned-fake-husband-turned-real-husband Henry, and we hoped they would be happy, but by Season 8 we should have known better. To make matters worse, he died in Cristina’s operating room. We saw how well Cristina reacted to having Derek’s life in her hands after the Season 6 shooting, and he actually lived. Having to watch Yang unknowingly operate on her mentor’s husband, as she flippantly talked about timing herself, and then watch her discover who he was after the fact, was one of the most painful deaths.

3. Lexie Grey

Sweet, loving, perfect Lexie was too precious for this world. Maybe it’s because a BuzzFeed quiz told me I was secretly Lexie because of my horoscope, or maybe because she was a giant ray of sunshine, but I don’t think I’ll ever be over Lexie’s death. When they introduced her as the other “girl at the bar,” I wasn’t sure how I would feel about her. Little Grey quickly worked her way into my heart, along with the hearts of all the rest of the characters, even McSteamy. Lexie died loving Sloan, and I wouldn’t have it any other way -- except maybe with them both living happily ever.

2. Mark Sloan

Derek’s best friend and also the reason his marriage fell apart, Mark was the guy we were supposed to hate. So when he actually shows up, for a little while we do. Slowly but surely, though, he wins back his best friend, along with us. From trying to take care of the pregnant daughter he’d never met, even at the expense of his relationship with Lexie, to the way he loved Sophia and Callie, to him telling Lexie how much he loved her in her final moments, we fell for McSteamy even faster than she did. Lucky for her, she never had to live without him.

1. Derek Shepherd

No matter how many surgeons died or left the show, this was the one we never expected. Derek was “the guy at the bar,” Meredith’s soulmate; he was McDreamy. They survived the deaths of their colleagues, the loss of their best friends, a mass shooting, a drowning, hostile uterus, a plane crash, and so much more. They were supposed to be the couple that lasted forever and he was supposed to die in her arms at 110. We thought they would face everything but their own deaths. We thought if anything would stay constant, it was these two. Instead of 110, he died at 49, and instead of old age he died a neurosurgeon with brain damage. The irony was missed on none of us.