This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Ikki Tousen
Ikki Tousen is mostly a Panty Shot series with lots of humor and action, but then Goei aka Hakufu's mom, after she met the happy and tomboyish Ukitsu... the girl destined to kill her daughter. She acted composed in presence of Ukitsu, but as soon as she was gone, the mother fell to her knees, in the verge of an Heroic BSOD. "How did Hakufu look when she left this morning? Was she happy? Was she angry? I gotta remember that... because it could be my last memory of her EVER..."
And we can't forget Chinkyuu's death in the anime. Ryoufu's reaction is heartwretching, specially when she kisses the dead Chinkyuu and leaves the hospital room, saying "You won't be alone for long... because soon, I will go with you!"
In the manga the above scene plays out differently, but no less heartbreakingly. After Chinkyuu is raped by Kaku's goons, and Ryofu realises that her disease is gonna kill her soon, she decides to go down fighting against her destiny. After a desperate battle against Myousai, she collapses and Myousai goes in for the kill, only for Chinkyuu to stop her at the last minute. Then, Chinkyuu is soundly thrashed by Myousai, and Sousou offers her the chance to join him and escape with her life. She loudly rejects his offer, and then crawls over to the fallen Ryofu, and while they talk, Ryofu finally dies. Chinkyuu then quietly takes off her and Ryofu's magatamas and breaks them, and then kisses Ryofu, killing herself at the same time. Her last words during that scene are quite heartbreaking.
Chinkyuu: We tried. There's that much. The magatama won. Again. But we tried. That counts. Maybe there's a better place out there. No magatamas... no fighting... I'd like that. Did I mention I'm going with you? Did you think you'd be rid of me so easily? Do you see Kaku? More importantly, do you understand? There are greater things than conquest, watch and learn. Together. We go together. Same's always. Ryofu... and Chinkyuu... Together.
Also from Dragon Destiny, the scene where Hakufu sees the spirit of her Disappeared Dad while inside her own mind. He tells her that it's not her time yet so she has to come back to the real world, and coupled with the somber music that plays in the background, this scene can be a real tearjerker.