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Tear Jerker: Arrow
Oliver waking up on the island to see birds going at his father's body. He desperately tries to drive them off then accidentally touches his father's dead hand and throws up from the trauma. Just the desperation in his voice is heartbreaking.
When Oliver first reunites with most of his friends and family. Especially when PTSD kicks in, and he nearly snaps his mother's neck when she checks on him.
When Dig is told that Deadshot/Lawton, the man who shot him that Oliver killed, was also the man that killed his brother Andy. Then worse, a good few episodes later, we find out Lawton's alive and Digg's reaction is to simply walk away.
The revelation that Diggle's former CO had turned from the strong, honourable leader into a bitter Soldier willing to use his skills to kill and steal because he thought that society owed him something. Watching him and Diggle at the diner gave you the vibe that Ted had been both his mentor and best friend. No wonder the poor guy couldn't pull the trigger.
When Tommy Merlyn states to Lance that he has no idea who the Arrow is. Despite Oliver showing him minutes before, you can tell in his voice he is not lying. He really doesn't know who Oliver is anymore.
When Helena shot McKenna. She has to stop doing what she loves and leaves the city to recover.
When Dinah admits to Laurel and Quentin that she was the last person who saw Sarah before she went on the Queen's Gambit and actually allowed her to go, the way she says that she let her daughter die is heartbreaking.
Felicity's reaction to not being able to stop the Savior from executing the District Attorney.
Roy, when asked by a murderous vigilante at gunpoint why he should be allowed to live, can't think of anything. He tells him to Get It Over With because nobody will miss him, even as Thea is watching the video stream and breaking down in fear for his life. And even when Ollie comes to the rescue, Roy is visibly shocked that someone would save him, much less shoot the man trying to execute him.
When Tommy figures out that Oliver still loves Laurel, Oliver confesses that, while he will always love her, so long as he's who he is, he can never be with her, and as such she can never know who he is. Double tear jerking, Tommy admits that, deep down, Laurel probably still loves him too, and if she did find out who Oliver was, she'd pick him over Tommy, so he packs his bags and leaves her, having to lie and claim it’s because he hasn't changed as much as they all thought, so as to avoid both of them getting hurt later.
The look on both their faces when Oliver explains to Laurel why he can't tell Tommy he's not still in love with her.
"It wouldn't be true. And I have enough lies in my life."
A major Cry for the Devil moment: Malcolm recalling the night his wife died, and how he could do nothing but listen to her die on his voicemail, over and over.
Oliver telling his family that Walter is dead, after Thea earlier described his disappearance as being just like Robert died. Thankfully he's alive.
Pretty much everything in "Darkness on the Edge of Town" for Moira: she's forced to finally confess her involvement in the Undertaking in front of Oliver and he walks away from her, Walter leaves her with Thea not understanding why and when the Undertaking comes to pass she'll have the blood of thousands on her hands.
Basically everything that happens to Tommy after breaking up with Laurel. Specifically, Ollie telling him to get back together with Laurel, only for Ollie himself to sleep with her and for Tommy to see it. If this series ends up depicting Tommy's Start of Darkness, he would be entirely sympathetic. For all his Nice Guy acts, something will screw him over. The guy cannot catch a break!
It gets worse for Tommy in the season one finale. He finds out the truth about his father, is made to listen to his mother's final message, and gets knocked out cold for trying to stop Malcolm from executing the Undertaking. But the worst part is he dies after saving Laurel when the second device goes off and starts destroying the eastern half of the Glades, and Ollie can't do a damn thing to save him.
and this is after a season of hinting that the first season would be his Start of Darkness. It's also the first time we've seen post-Island Ollie truly break down. He can handle his emotions about Laurel - it's what helped him get through the island. And of course he feels nothing for the bad guys. But Tommy ... Tommy's just an innocent who got caught up in bad things. And he's his best friend.
Ollie: It should have been me. Tommy, open your eyes.
Felicity's reaction over not being able to stop the second earthquake device.
By the end of the season one finale, everything's just fallen apart for Oliver. His mother's arrested after outing Malcolm and her involvement in the Undertaking, his best friend dies before him, and he couldn't stop the Undertaking entirely. Meanwhile Diggle's critically injured and had to be left behind in Ollie's failed desperate run to save Laurel/Tommy and Felicity's all by herself at the club, also affected by the earthquake. By the end of the episode, the east side of the Glades is still falling apart, and we don't even know if Thea made it out of the Glades in time. The Offscreen Inertia's going to kill us before the show starts up again.
It's revealed in "Identity" that Diggle has broken up with Carly, unable to reconcile his feelings for her with his hatred towards Deadshot and knowing he's still out there.
It's swiftly established that Laurel, the Hood's biggest supporter in the first season, has turned on him since the destruction of the Glades. "Identity" reveals that Laurel blames him for everything that happened in the previous season's finale, from Tommy's death to the earthquake machine that destroyed the Glades, all because she went back into the C.N.R.I. building to look for Tommy and found his dead body impaled on the wreckage of the building whilst the Hood simply walked away.
In "Broken Dolls", Laurel realizing she was wrong to blame the Arrow for Tommy's death, because it was really her fault if anyone's, and breaking down crying in her father's arms.
It's difficult to watch Quentin's complete despair as he hopelessly tells his daughter to close her eyes as the Dollmaker embalms her alive.
Quentin: I'll kill you you son of a bitch! I'LL KILL YOU!
In "Crucible", Quentin goes to Oliver to plead with him to try and help a rapidly degenerating Laurel. Not only is that tragic, but Sara listens from the other side of a door and hears her father describe how they were hurt in the aftermath of her "death". Her reactions are heartbreaking.
If that wasn't enough, Quentin is in tears at his support group, as he relates what's happening to Laurel. He sees her life falling apart the same way his did, and there's nothing he can do.
This episode has a ton of it. Earlier, Felicity's almost in tears because Oliver's life ...
Felicity: Don't you have any happy stories?
No, he does not.
Oliver:THESE ARE FIVE YEARS! Five years! Where nothing good happened!
In "League of Assassins" Sara's reunion with her father, and then, her being forced to get away from him to save her family's lives.
In "Keep Your Enemies Closer seeing Slade struggle with severe burn injuries is very jarring.
Also, Felicity's reaction to Oliver's one night stand with Isabel. When she finally asked why he did it, it is a very bittersweet moment. First, Oliver goes with the more flippant answer "It just happened." then checks himself and realizes that he's talking to Felicity of all people and explains that while being The Arrow, he can't be with someone that he "could really care about." When she walks away, you can tell from his expression, he knows exactly what he did and is actually sorry for hurting one of his closest (one of two) friends.
God knows what went through Ollie's mind in "State v. Queen" when he ended up killing the Count after Felicity's life was threatened. He's so stunned about what he did he couldn't even compose himself around Thea, and even after sitting through his mother's verdict and going back to HQ the shock hasn't gone away.
In "The Scientist" Barry Allen's backstory. When he was 11, someone he describes as "a blur with a person inside" attacked his house and killed his mother. Before he could do anything to help, he was twenty blocks away from home in seconds flat. When he tried to tell the police what had happened, everyone thought he was just covering for his father, who was blamed for the crime and given a life sentence. The fact that this is the reason why Barry looks into strange cases hammers it home. And there is also the fact that it's heavily implied to be Professor Zoom, Barry's Arch-Enemy in the comics. Let me just sat that this will most likely not be the only time Barry's life gets screwed over because of him.
Slade Wilson's death by Mirakuru injection is arguably one of the most disturbing and tear-jerking moments in the show thus far. Manu Bennett's award-worthy performance is tragic, watching his character go through all this agony to the point that it becomes incredibly hard to watch.
In "Three Ghosts", Shado's death, and a freshly resurrected Slade's reaction to it. Extra points for this being implied to be one of the reasons that turn the Slade from the island into present day's Deathstroke.
In "Blind Spot", Laurel's attempt at uncovering the truth about Sebastian "Brother" Blood leads to her being publically humiliated when Blood uses his connections to have Laurel's place searched legally and get her arrested for illegal possession of a controlled substance, which subsequently discredits her when she correctly asserts what's happened to her father, who's unable to trust her because of her lying about her pill addiction.
There is also Roy, who almost beats a prostitute serial killer to death and hits Sin during a stakeout because of a Mirakuru-induced loss of control. First, he can't explain what's happening to Thea, and ends up hiding to cry in the hospital. Then, during a visit from the Arrow, Roy asks him to kill him. Thankfully, Ollie has other plans for him.
In "Tremors", Roy and the Arrow are in Malcolm's old mansion looking for Bronze Tiger. Before Arrow can order Roy not to touch anything, he has time to find a picture of Tommy. You can see that Ollie has to make at least a small effort to contain himself in front of the kid.
Also, Laurel's situation has become so bad that Ollie is willing to tell Sara to come back to Starling at the risk of a return of the League of Assassins, too.
Laurel at Verdant, for that matter. She's clearly hit the booze hard and is taking cheap shots at Oliver and Thea, and casually mentioning how she's likely going to be disbarred. Watching her unravel like that is painful.
Slade's brief reversion to sanity after Ollie reminds him of Shado. He breaks down a bit once he realizes what the Mirakuru is doing to him.
"Heir to the Demon":
Oliver, after learning from Felicity that Moira's been lying to him about Thea's true parentage, gives her a "The Reason You Suck" Speech and disowns her as his mother. Despite bringing it on herself with one lie too many, Moira's face when she realizes Oliver won't even let her get near him is hard to watch.
Oliver delivering his introduction speech for his mother right after Felicity tells him what's going on. You can see he means every single word, just not the way they were written. He struggles to get through the speech and you literally hear the moment he's made the decision to lie for Thea's sake.
Oliver tells his mother he knows what her secret is on-stage at a political rally. Her face drops while she's still turned away from the audience, and in the next second, both she and Oliver are all smiles with Thea none the wiser. A detailed illustration of how epically screwed up the Queen family is.
Felicity's anguish over being torn about whether or not to tell Oliver the truth is equally heartbreaking. Especially when you find out that Felicity wasn't just worried about Oliver hating her, she was worried that she would lose the pseudo-family she had built in Starling City, and relive the trauma of her youth.
The flashback to the night before Sara sneaked onto the Queen's Gambit — we see Sara try to reason with Laurel that planning her entire future around marrying a notorious womanizer like Oliver Queen isn't exactly the best idea, only for Laurel to snap at Sara and call her a bitch trying to sabotage Laurel's future. As Sara walks away, she sends a text to Ollie confirming the plans for the next day, and a quick glance at the message history between the two reveals Sara was having second thoughts and Ollie was practically begging her to betray Laurel; ultimately, it was Laurel herself who nudged Sara into making the wrong choice.
Dinah sobbing and screaming for Sara as Quentin pulls her away. Thankfully, it's not a permanent departure.
While their parents happily welcome Sara home, Laurel drunkenly blames her for all the pain their family's been through since her "death", going so far as to accuse her of stealing Laurel's life away, and kicks her out of the apartment, even throwing a glass at her. The looks on Sara, Quentin, and Dinah's faces say it all, and Sara's glance back at her parents as she simply says "I'm sorry" doesn't help either.
We get a flashback to the moment when Moira told Quentin and Laurel that Sara had been on the boat. It's as sad as it sounds.
"Time of Death":
Oliver finally confronting Laurel — the two have a pretty harsh argument, accusing each other of wrongdoing and throwing mistakes in each other's faces. Laurel blames Ollie for sleeping with Sara in the first place, and now again, but he shuts her down by yelling that she has no idea what crap his family is going through, that she's dead wrong to think she's the only one who's been suffering, and taking a very harsh but well-deserved stab at her substance abuse. What makes it more sad than just mean is Oliver professing that he loved Laurel for half his life, but he's tired of chasing after her and taking all the blame, and how Laurel herself comes to realize how horribly she's been mistreating others rather than blame herself. The scene has the emotional weight of both a sad breakup and someone washing his hands of a failed intervention for someone very close to him.
Tockman's calm, confident façade crumbling as he begs Felicity to let him steal the money to help his sister.
The Reveal that Ivo wanted the Mirakuru to heal his wife's Alzheimer's disease. The tragedy of such a noble goal resulting in his horrific actions and deranged personality adds a quite unexpected depth to his whole story.