Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Tear Jerker: Black Butler
Black Butler is filled with tearjerking moments and downer scenes.
In the anime, Ciel appears downright cruel and malicious at times, although in the manga, he is simply bitingly icy and elitist. It's eventually revealed that he was a happy, loving and carefree child, though sickly and shy. Then his parents (and pet) were murdered, their mansion set on fire, and he was kidnapped. He was locked in a cage with other children his age to be a child sacrifice until he called upon a demon in his desperation to live. He shortly after unleashes terrible revenge on those who he felt wronged and humiliated him. All before turning eleven.
A particular moment in the manga triggers Ciel to suffer an intensely brutal PTSD attack. Heartbreaking stuff.
In the manga, "Would you like an orange, sir?" said the poor little girl with freckles. After a particularly nasty moment, Ciel's grasps at redemption were hopelessly despairing to see.
The whole of the manga's Noah's Ark Circus story.
In chapter 44, watching Maylene and Finnian's breakdowns after it seems to seriously and completely dawn on them that Sebastian is dead is utterly shattering Luckily, Sebastian is not really dead.
Episode's 7 and 8 of the second season in which Alois, who before seemed like a complete jackass, is stabbed and ignored by Claude for a bit who's busy practically orgasming over the taste of Ciel's blood. Alois's tearful response "Oh, you look like you've seen a bunch of maggots squirming in a dung pile" to Claude's indifference towards him, we learn his backstory where his little brother died and left him alone, and he practically confesses his love for Claude, telling him he's the only one he has left in the world, before Claude tenderly holds his face and stabs him to death.
In Episode 11, Alois (in Ciel's Body) asks Hannah to tell him that she loves him and give him a hug, which he's ALWAYS NEEDED. She does both, which prompts him to cry tears of joy and say "Love is...warm, isn't it?" Pass the tissues please.
Madame Red's death at the chainsaw of Grell, and Ciel's reaction. "Red is... your favorite color".
Her horrific backstory as well. Yikes.
From the Alice in Wonderland OVA, Madam Red played the Queen of Hearts and after the trial Sebastian saves Ciel from being beheaded. Suddenly, Madam Red is wearing her normal clothes and smiles sadly. And then, to twist the knife further, she says this:
"So, you're going home. I hope we can meet again in another dream."
Madame Red's funeral. Ciel placing the dress on her corpse is an "aww" moment.
The house servants having to put down poor Pluto.
Chapter 57. Elizabeth is about to be seemingly killed by a horde of zombies. "I wanted you to think I was cute, up until the end..." Cut to shot of Ciel's anguished face.
Elizabeth's backstory in chapter 58. At first, we see her as a genius at fencing, but Ciel doesn't know that and is happy to marry just plain sweet Elizabeth, and she promises to be a wife he can protect. Then when Ciel returns with Sebastian and she realizes she's now taller than him, she wishes to be a wife to protect him.
The end of the second musical. Eric's willingness to do anything to save Alan in itself is pretty tear-inducing, but it gets even worse when Eric ends up not only failing, but also being the one who kills his friend, shortly before he is killed by Sebastian.
Cue emotional music as Sebastian and Ciel comments on the snow-like souls being released from Eric's body, and states how "there is no meaning in life and death, however beautiful things... are simply beautiful." as Alan and Eric stands up and walks together to the back of the stage.
Chapter 61. When Sebastian is stabbed by the Undertaker; especially when Sebastian reaches out to grab Ciel's hand, but then gets a giant death scythe through his body. Cue the beginning of a dramatic flashback.
The scene in Chapter 41 where Ciel straddles Sebastian's supposedly dead body, buries his face in Sebastian's throat and insists his butler was never to leave his side is comparable to a boy mourning his beloved dead dog.
Finnian's very harsh backstory. It depicts him in a room with a barred window with sunlight and a little bird chirping before flying off..cue him on a dissection table with a syringe going in him as he screams and cries and begs for the people to not hurt him. Then he runs off and bumps into Sebastian and he, for the first time in his life, is actually surprised that him rushing into Sebastian didn't hurt him. Even if he doesn't know that Sebastian is a demon, he looks so relieved that he's not considered a monster for those horrible treatments.
The deaths of Lau and Abberline in episode 20. Though Lau comes back somehow in the second season.
Maria, Abberline's to-be wife, reads about his death and receives merely a handful of toys as compensation.
In the last scene of the seiyuu event, Kuroshitsuji Red Valentine, we're treated to what would have occurred had the second season never happened. Sebastian, with the contract ended, has eaten Ciel's soul, but he's not happy as one may think- he quite obviously misses his young master. The scene opens on Sebastian having made a cake for the now dead Ciel, and carries through him coming to grips with the fact that there's no manor for him to protect, no young master to serve, there's nothing left for him. This apparently takes place only a day after the end of the contract, as Sebastian says, despite in the past having seen a hundred years as no more than the blink of an eye, a single day can seem like an incredibly long period of time as well. It ends with Sebastian's famous "I'm merely a butler/I'm a devil of a butler" being twisted into "I'm merely... alone/I'm a lonely devil".
Sebastian: Like falling snow... Everything disappears, before you can savor it.
It could be considered a borderline tearjerker when Agni refers to Sebastian as his friend. His genuine surprise that he would label him as such may indicate that Sebastian has never had a friend before (his being a demon aside) and is happy to be considered one. Life as a demon may be lonely for Sebastian.
Depending on your point of view, any scene which shows the deep trust and appreciation the servants of the Phantomhive household have for Sebastian (or Ciel, again depending on your point of view) can be soul wrenching to know that the person/people they care about is nothing more then an illusion created to manipulate them. The same goes for anybody who befriends Ciel while he's undercover- namely Doll, since she trusted him deeply and learns the truth in the worst way possible.
During Elizabeth's flashbacks in chapter 58, her mother slaps her when she complains about having to fence wasn't "cute". Cue a combination between a tearjerking and heartwarming moment between mother and daughter. It goes to show that Francis, despite all of her cold aloofness towards her family, she truly does care for them and seems to want to protect her daughter and Ciel in any way possible given the Phantomhives' unfortunate profession.
Elizabeth: I don't want to practice the sword anymore! Swords aren't cute at all!
Francis: I know it's hard, but it's for his sake and yours. You understand, don't you?