LaFontaine and Perry's argument in episode 26, especially when it comes around to LaFontaine's gender identity.
Perry: ...or why you won't even let me call you "Susan" anymore! LaFontaine: I don't wanna be "Susan" anymore! Perry: Well, that's too bad, 'cause she was my friend! I don't even know who you are anymore! (Perry storms out) Laura: ...You okay? LaFontaine: ...Peachy. My best friend since I was five thinks I'm some sort of freak.
"Go away, Carmilla. Go run and hide. We're done."
"We won. We actually won. We won, and...Carmilla's dead."
Even though he acknowledges Will had it coming, Kirsch is visibly miserable after Will's been staked. It's hard not to feel bad for the poor guy.
"When the chips are down, you're kinda like a bro... and I could sort of use one..."
The season one finale. Carmilla's alive and well enough to embrace Laura, which is very sweet...until you see Danny standing in the background, and Perry has to gently lead her out..
And though it's quickly followed up with the reveal that Carmilla is alright, hearing and seeing Laura start to cry as soon as she starts talking about Carmilla is heartbreaking.
Laura: And look, I know that she was a terrible roommate, and...kind of a terrible person sometimes, and that one big, grand gesture doesn't make up for centuries of what's essentially murder, but...she was my terrible roommate, and...she made the big gesture for me.
Perry's Sanity Slippage throughout season 2. She's been sharper and harsher towards Carmilla, horrible things keep happening to her, and now she and LaFontaine are on the outs too, because LaF reanimated a dead corpse to give JP a body. And according to their in-character Twitter accounts, things don't seem to be getting any better.
This tweet from LaFontaine's Twitter.
I hate that Perr won't talk to me. It feels like half of me has been cut off.
Everything from about the second minute on of season 2 episode 22. Laura bites out an exhausted "I don't care." For a girl whose defining trait is literally caring about everything, being exhausted to the point where she cares about nothing but getting some sleep is a major defeat. And then comes the conversation where every Creampuff's heart got ripped out. And Carmilla tells Laura how to kill Mattie, and trusts her not to use it except in a situation of life and death.
Season 2, episode 27 more or less ripped the Hollstein shippers' hearts out. After admitting she's not sure whether or not drinking Lophii's blood would've killed her, Carmilla asks Laura if she would've cared if it had. Laura, hurt, says that of course she still cares for Carmilla, and can't stand the thought of anything happening to her... and then Carmilla kisses Laura. Laura responds, but pulls away, and says, "I can't," because a part of her still wants Carmilla to change, and she knows that isn't fair to Carmilla. And even though Carmilla says she doesn't care about that, Laura does.
2.30. Mattie, the 1,200 year old vampire, dies in Carmilla's arms after Danny crushes her locket. This sends Carmilla spiraling into a Despair Event Horizon:
"God, she was right. You are a selfish, callow girl, and I am the fool who trusted you. Three-hundred years of friendship... can you even imagine? We saw Electra in Paris in 1709, the ruins of Pompeii, we watched the Moon Landing all those memories, all that life to end like this? For what? For you? ...'Be good for me, Carmilla. Change for me, Carmilla! Burn down everything you've ever loved for me, Carmilla.' The next one of you who comes near me, I swear to God, I will kill."
2.35. Danny dies. By being literally stabbed in the back. Even Mel was completely disgusted by this. Danny dies in Laura's arms, while Kirsch, weakened and bleeding, can only sit there and watch in horror, only hurting himself further when he tries to lunge at Theo to avenge Danny. Danny's last words are assuring Laura that she's not afraid. Christ.
The hollow and empty look on Laura's face at the end of the episode which makes it clear that Danny's death has pushed her over the Despair Event Horizon. She's not even fazed by Vordenberg sticking his head through the door and announcing he will kill Carmilla.
With Kirsch and Danny firmly settling into 'best bro' territory nearing the end of the season after he accepts the fact that she doesn't like him in a romantic sense, his brief glee that she has been resurrected only for her to attack him to drain his blood can be rather upsetting.
The look Carmilla gives Laura when the latter saves her from being executed by Vordenberg is heartbreaking just because she looks like she didn't think Laura would do it.
Perry is season zero is cheerful, optimistic, and not only believes in the supernatural, but eagerly seeks it out and actually came to Silas because of it. Compare that to the Perry we met in season one — neurotic, jumpy, and knee-deep in denial about the supernatural things going on at Silas. Just... what happened?
Past!Carmilla telling Past!Perry she "just isn't that special" after her spell attempt fails. And since Carmilla knows the supernatural is very much a thing, her taunting of Perry seems rather mean spirited.
LaFontaine talking to an unconscious Perry/Dean as they wait for midnight so they can attempt an exorcism. LaF just misses Perry so much. To twist the knife in, the Dean tries to pretend for a second that the exorcism worked to trick the others into setting her free. It very nearly works, too. Carmilla intervenes before they can let her go, but it's just so heartbreaking. For a moment, it really looked like we had our Perry back...
The revelation that part of the ritual to end the world requires the Dean to sacrifice things she cares about is a twofer. Firstly, the fact that the Dean intends to use Carmilla as one of her sacrifices shows that in her own twisted way, she does care for Carmilla as more than just a tool. On the other hand, it lends a darkly ironic twist to Carmilla's entire situation. If Carmilla had just let Laura be sacrificed to appease the Anglerfish in Season 1, she'd have been safe, at least for another 20 years.
Alt-Carmilla. Carmilla in a parallel universe where she gave Laura up to the Dean at the end of season one. Carmilla in this universe has clearly gone a little crazy, and is constantly tormented by guilt and heartbreak. When she hears Laura's voice, her reaction implies that she's hallucinated it before. Mattie being almost completely unsympathetic doesn't help.
JP dies and there looks to be no backup this time.
Laura's sacrifice. It doesn't help that she dies talking about plans she had for the future as Carmilla holds her and cries.
Who thought The Dean of all people would have a genuine tearjerker moment? Once she realizes she messed up her spell, she dissolves into a breakdown that slowly turns into nightmare fuel.
"Where are you?! I have descended into Hell! I have made myself a beggar and a slave! YOU HAVE TO BE HERE, YOU HAVE TO!! GIVE HIM BACK TO ME!!
"How dare you? How dare you? You think I want to be mortal now?!"