When Benton's mother dies. Throughout the entire season, we've come to know him as a very stern, stiff, gruff character whose only weak spot is his love for his mother and his complete denial about how ill and frail she's becoming. Towards the start of the episode, we've heard him give a patient's relative a very standard, "I'm sorry" speech. Then he's paged about his mother, rushes to her nursing home, only to get nearly the exact same speech from her doctor. When her physical therapist comes to comfort him, he finally breaks down and cries in her arms.
A subplot of "Love's Labor Lost" has Benton bringing her into the hospital after she falls down the stairs. As the nurses try to undress her, she frantically tells them, "No! Not in front of Petey!". Frail, elderly, and possibly developing dementia, and she still has enough dignity to not want her son to see her naked.
"Love's Labors Lost". That is all.
A little girl who had recently been adopted from an Eastern European orphanage is abandoned in the ER by her mother because she's HIV positive. Carol wants to adopt her, and meets all the criteria, but is turned down because she tried to commit suicide last year. She's devastated and, to make matters worse, the adoption was so close to being approved that she'd asked Tatiana, the little girl, if she'd like to come and stay with her.
What's more, after the adoption denial, she goes running not to her fiance, but to ex-lover Doug, essentially revealing that she's still in love with him despite how he broke her heart, and he has to struggle not to take advantage of the situation as he's clearly still in love with her.
The transgender patient jumping off the roof in "ER Confidential".
Doug's girlfriend catches him with another woman and angrily breaks up with him, dismissing all of his apologies and pleas for a second chance. It culminates in him desperately declaring, "It won't happen again" and her sadly responding, "Yes, it will."
Carol's fiance's speech to her on their wedding day when he describes how much he loves her—"Every day, I thank God for bringing you into my life"—then asks if she feels the same way, thus forcing her to admit that she doesn't. It really says something for the show's quality that it could make you feel sorry for a Bland Perfection Disposable Fiancé that the viewer isn't supposed to care about.
The death of paramedic/firefighter Raul in season 2.
When Mark runs to Union Station to catch Susan and tell her that he loves her, only to have her reject him.
Reese Benton being born, so weak and frail and near the edge of death.
In "Fear Of Flying", Benton botches a surgery on a neonate, leaving her critically ill. He hovers over her bed and tries to receive the 23rd Psalm, but symbolic of his error, he can't remember the words.
In "Family Practice", Mark and his father, a Navy veteran, are at a VA hospital's ER after the latter had suffered a COPD episode, when a mass-casualty trauma arrives, the result of a helicopter crash. The pilot, who is stable when they arrive, is visibly distraught over the accident. Capt. Greene does all he can to re-assure him while three of his crewmates are coding all around them. Then suddenly, the pilot stops breathing as a pneumothorax (pressure from a collapsed lung) suppresses his heart.
This episode has a few other minor Tear Jerkers as Mark and his father deal with his mother's dementia, and work through their own strained relationship. Fortunately, when Mark is asked to assist with the helicopter crash patients (beginning with giving the pilot CPR and assisting in relieving his pneumothorax, reviving him), this allows him to see the pride with which his father watches him work. It leads to a heartwarming moment toward the end when they finally have a talk, and come to understand one another.
In one episode, Carter accidentally resuscitates an old woman who had a do-not-resuscitate order. At the end of the episode, he observes the woman as she dies. Lucy comes in and notes what treatment they normally would give at each stage as the patient's ECG degrades to asystole. While he handles it professionally, it's clear he's near tears.
The ending of "The Storm, Part 2". Carol tearfully begs Doug not to leave, telling him "I don't want to wake up alone tomorrow." Nearly in tears himself, Doug plants The Big Damn Kiss on her, makes an Anguished Declaration of Love, and walks away, leaving her sobbing in the hallway.
In "Responsible Parties", a kid in a car accident on the way to prom ends up with 80% third-degree burns. Lucy is clearly distressed as she holds a phone up to him so he can speak to his parents (who are en route to the hospital) on their car phone.
"Dad? I don't think I'm gonna make it out to the lake this summer"
When Lucy died in "All in the Family", because even that bastard of a doctor Romano refused to give up on her when she was clearly beyond help. The worst part is that at one point it looked hopeful, before things took a turn for the worse.
The desperate way that he reacts when she's gone, trying to go for another cycle, anything to have a chance. Elizabeth's quiet acceptance of Lucy's death is heartbreaking, but who thought they'd see Romano trashing the room because he couldn't have a colleague? He genuinely liked her, because she was smart, gutsy, and stood up to him.
After Lucy's death, a letter arrives which reveals that she was matched to the hospital and would have become a psych resident.
Mark's father dying at the end of Season 6. At this point he has end stage Lung Cancer and is finding it very difficult to breathe. Mark gives him a sponge bath and his father tells him that he used to bathe Mark as a baby. He then says "I love you, Mark" in the saddest way possible, to which Mark responds "I love you too, Dad." Mark then takes a nap and when he wakes up his father is dead.
Benton flat-out begging his ex Carla not to take Reese away from him, telling her that he means more to him than anything—"I'd lay down in front of a train for him. THAT'S how much I love him."
The Season 6 arc involving Kerry's beloved mentor Dr. Lawrence, who's developed Alzheimer's—specifically, his discussion with Kerry during his final appearance:
Lawrence: I saw a woman this morning - dementia. She had no idea where she was, who she was. In ten years that'll be me. Bedridden...in diapers. Locked away in some home, nobody coming to see me. Kerry: I'll come and see you. Lawrence: But I won't know who you are.
Kerry crying in that scene, particularly as she said earlier in the episode that she thinks of him as not only her mentor, but her father.
After everything that Lucy did to make sure that Valerie lived long enough to receive a heart transplant, she has a stroke and ends up in a persistent vegetative state during the surgery. Lucy is devastated and blames herself, while even Romano tells her not to blame herself.
One of Lucy's early conversations with Valerie has them talking about how Valerie would be graduating soon if she had stayed at university and how Lucy is. Neither of them survive until then, with Valerie dying in her next episode, and Lucy being stabbed to death in the February.
Happy tears at the end of "Such Sweet Sorrow" when Carol and Doug reunited.
In "The Visit", Benton's nephew Jesse gets shot. Benton does absolutely everything he can to save him. Finally, when Mark states that Jesse's chest cavity is filling with blood and Elizabeth sadly points out that he's oozing everywhere, Benton starts to fall apart and desperately says, "Come on, Jesse. Come on, man, don't give up on me. Jesse. Come on, man. Don't give up, please. Come on, Jesse." Jesse finally dies from his injuries. Jackie's Big "NO!" over the loss of her son and the way she and Benton cling to each other as they cry make it all the more painful.
The flashbacks to the death of Luka's family. His son is already dead when he gets there, and his daughter stops breathing. Luka spends hours performing CPR on his daughter, hoping that help will come, and only stops because he's exhausted. Then he checks his wife's pulse and discovers that she's died while he's been trying to save his daughter.
In "Piece of Mind", while Mark is recovering from his brain surgery, he's keeping an eye on a child he befriended that has in for the removal of a tumor on his heart. He can only watch helplessly when the boy suddenly begins to bleed out, then the doctors rush in to crack his chest back open and try to fix the complication. At the end, all they can say about the boy is that it's "touch-and-go". We never find out if he survived.
Maggie (Abby's mum) getting put in restraints. It's quite heartwrenching, especially if you know someone who's suffered from bipolar themselves.
Abby's entire childhood, which is revealed during Maggie's first arc. Abby had to find ways to trick the neighbours into giving her food so that her and her brother wouldn't go hungry when their mother was in a depressive episode. Abby also reminds her of a time that, after discovering that Abby had been to see her dad when she was 10 years old, Maggie chased her around with a knife. Considering that she screams at Abby and calls her a 'little bitch' while being put in restraints, it's pretty heartbreaking to imagine what it must have been like for Abby to be on the receiving end when she was a child.
"I'll Be Home For Christmas". Having just lost custody of Reese, his stepfather Roger struggles to hold back his tears, obviously not wanting to upset the boy. It's easy to feel sorry for someone who really hasn't done anything wrong and now has to contend with losing both his wife and his stepson within a few months. Luckily, he'll still get to see Reese occasionally, but it's still painful.
"Damage is Done" is full of them. As the episode starts Rachel is happy to take care of her baby sister Ella, and offers to make Elizabeth something to eat or drink while she's sick. Then Ella gets a hold of ecstasy pills that were in Rachel's backpack. Mark gets told of his daughter coming in with an overdose and hurries down to the ER, panicked over Rachel whom he naturally assumes is the one who took the pills, and is completely stunned and shocked when he walks into the trauma room and sees Elizabeth and Ella. But most of all it's Rachel who gets your tears flowing. Clearly she loves her baby sister and she is both frightened, sad and shocked over what is happening. When Mark lays into her for keeping drugs in the house where the baby can find it, and explains to her exactly what damage Ella might suffer, she breaks down, needing her father in that moment just as much as Ella does.
Mark dies knowing full well that he can never be there for his daughters during their formative years. To add insult to injury, Ella's first word is "Dada."
Dr. Burke, who successfully removed his first tumour, gives Mark the death sentence and says "You should have been dead a year ago, Mark. You got married, you saw your daughter be born. I'd say that was time well spent."
The look on Carter's face after he finishes reading Mark's letter to the staff can still give one chills, as well as his near-breakdown as he reads Elizabeth's.
Romano throwing himself into performing surgery on a little girl with a tumor in one of her lungs, talking about how cancer eats you alive, and listing off types and how it even kills "little girls, fathers with little girls," with the implication that he's working so hard because Mark couldn't be saved.
Kerry tearing up as she reads the eponymous letter and later having to leave a patient to break down crying.
Abby and Carter talking about how many lives Mark saved, coming out with an estimate of two or three thousand people, basing it off him saving one or two people per shift, five days a week, for ten years.
Elizabeth's reaction during Mark's funeral in "On the Beach". No screaming or wailing—just quiet, wordless, complete devastation. Bravo, Alex Kingston...bravo.
Kerry telling a deaf patient about her miscarriage through sign language.
Sandy's death in Season 10 was played for mass quantities of Narm, but largely saved by Laura Innes' performance. Kerry's quiet desperation as she pleads with the surgical team to let her into the OR ("You have to let me see her...that's my wife in there") is devastating, especially for a character who's spent her career being as abrasive and unlikable as possible. Especially at the very end of the OR scene, where blood begins running up Sandy's endotracheal tube (that's it in a surgical situation), Kerry's face freezes in position and she quietly tells Elizabeth and Anspaugh: "You can stop. She's gone."
And her awful day gets capped off by Sandy's suddenly homophobic family essentially kidnapping their son and refusing to hand him over to her, with her brother all but throwing her out of his house.
The stillbirth of Carter's son. He staggers out of the delivery room, only to hear his father call his name. He turns, sees him holding his arms out to him, and staggers over to him, collapsing in tears.
Later in the episode, Carter and Kem grieving together.
Ben Hollander, an old depressed man going blind, and his short-term relationship with Susan Lewis.
"Time of Death", with guest star Ray Liotta as a dying alcoholic ex-con. The whole episode is in real-time, and goes back and forth between his subconscious and scenes in the hospital. He ends up refusing surgery that might save his life, and Pratt (who never knew his father) takes his final request to get in touch with his estranged son.
The episode ramps it Up to Eleven when the son coldly rebukes the father over speakerphone; the staff in the room are shocked to silence as the father quietly weeps.
"Two Ships", when two planes crash in mid-flight above Chicago:
A kindly old man Neela was talking to before she ran into a burning building was wanting to find his dog. When Neela gets back, she sees the dog beside him and happily tries to talk to him about him having found it—only to be told that the man died. Shocked, Neela can only say that she was talking to him a minute ago.
Adrian's death. He doesn't have a pulse, but CPR is keeping oxygen flowing to his brain, so he's still conscious. Pratt, Ray and Sam manage to keep him alive long enough for his family to get there, before he asks them to stop. It's the Single Tear that does it.
Neela watching the video Gallant left her and finally breaking down.
Earlier on, Frank's reaction when the military cops show up looking for Neela. With just one look (no doubt gleaned from his own experiences in the military), he knows why they're there and what they're going to tell her.
The ending of "21 Guns". As well as the Adult Fear of something happening to your pregnant partner — for all Luka knows, he's watching his wife and child die again.
The death of Pratt in the final season premiere. He and Abby had been injured in an ambulance explosion. They try their hardest to save him, but his carotid artery bursts, killing him. The most heartbreaking part is his little brother, a paramedic who only first met him when he was 18 (4 years before), begging them to keep him on a bypass machine a little while longer when the doctors know he's already far beyond hope. What follows is a practical honor guard as Gant is wheeled to the elevator to be taken to surgery for his organs to be harvested for donation—Frank rushes ahead and presses the elevator button. A menial task he would otherwise have complained about, but clearly felt obligated to do for Pratt's sake.
At Greg's memorial service, it is announced that his organs have gone on save several other people's lives.
"The Book of Abby". Specifically, Haleh's hidden wall◊ with the nameplates from departed staff.
"Heal Thyself", where Dr. Banfield desperately tries to save a girl who had drowned. It's revealed that her son had died in that very trauma room several years before while they were on vacation in Chicago. Scenes from the present day, and from her son's death—where Dr. Greene tried to save him—are shuffled between. While her son, who had a history of seizures, had suffered a massive stroke that was actually caused by undiagnosed leukemia (whose signs she had previously ignored because of the aforementioned history of seizures), Dr. Banfield theorized that the girl wasn't responding because she got into her uncle's medications. She is able to reverse the overdose, and save the girl. At the end of her episode, she finally opens up to her husband about her feelings after their son's death, and allows herself to grieve.
A mild additional Tear Jerker places when in Dr. Greene's history this takes place: he has to postpone a chemo treatment for his recurrence of brain cancer during the code for Dr. Banfield's son. He's frequently shown favoring his left temple during the episode. Dr. Romano makes an appearance, telling him he "used all his influence" to keep a chemo suite open for him. Then he makes a crack about his cancer:
On the November 13, 2008 episode "Heal Thyself", Eriq La Salle gave a speech before the episode's cold open remembering Michael Crichton, who helped create the show. Made all the more saddening because the episode it prefaced was the one that featured the return of Mark Greene via flashback.