This is based on opinion. Please don't list it on a work's trope example list.
Tearjerker / Dance in the Vampire Bund
The Heroic Sacrifices of the Lords of the Earth Clan, as well as their reasons for giving their lives. Their liege-lady, Queen Lucretia, was killed and they lived for centuries afterwards, despising themselves for what they saw as their greatest and most unforgivable failure, but they lived on for the sake of Lucretia's daughter Mina. And finally, when they realize that Akira can protect Mina better than they can, they sell their lives to let Mina and Akira escape. Lord Connery takes a spear meant for Lord Ernest, even though none of them were going to walk out of there anyway, just because he doesn't want his friend to die before he does. Each of the Lords of the Earth Clan die with a smile on their face, content that they've done all they could and glad that they can finally see their beloved queen again.
Alphonse is a walking tearjerker in volume 14. His backstory is revealed and the seemingly coldhearted, treacherous bastard is revealed to be a Stoic and Iron Woobie, and the depths of his love for Mina and his sheer nobility are almost staggering. He new Mina when he was a child and found himself falling in love with her. However, he soon realized that because of his family's Legacy of Service, he could never be with Mina, and so devoted his life to serving her. His initial betrayal of Mina, when he proclaimed the fake Mina as the true vampire queen, was spurred by a single moment of weakness in which he desperately hoped that the fake Mina could love him, and he spent the rest of his life regretting it. He constantly worked undercover to further the real Mina's cause and sabotage the efforts of the fake Mina. Throughout the entire series, he treated Akira like shit just to push him to become better, and when he's finally satisfied, he forces Akira to kill him to end the life he had grown tired of. He then destroys not only his own reputation but that of his family by taking responsibility for all of the shit fake Mina caused in order to protect the real Mina from the political repercussions. And his final wish? To be reborn as a flower that Mina could wear in her hair before it wilted at the dawn. He gets his wish.