This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Lone Wolf and Cub
Quite common. In one particularly notable example, Itto gets an assignment to take down O-Yuki, a female fighter who has gone on a killing spree through the ranks of a feudal lord. During the encounter, Itto finds out that she is killing the many samurai in order to draw out a samurai officer who previously raped her. Even though he is bound by contract to kill the woman, Itto compares her quest to his own and stands back, allowing O-Yuki to kill her tormentor, getting her revenge. Out of respect she then faces Itto in formal duel, even though the result is obvious. After having slain his target, Itto states that she can finally be at peace "in a place where nobody will ever harm her again". He then grants her a warrior's funeral and sheds Manly Tears.
Ittou's speech to Daigorou shortly before the final battle. ("Though my eyes shut, my lips close... do not fear. In that world of rebirth, I'm still your father. In that world and all worlds, *you* are my *son* !") Daigorou remembering this speech at the end of the battle, when realizing his father is dead, is even worse.
At one point Itto passes through the lands of his former student Lord Masatsune, who has been ordered to stop him at all cost. No points for guessing how that works out. The scenes of slaughter are contrasted with flashbacks of the two in happier times, finally culminating with Itto facing his former student and acknowledging him (posthumously) as a full-fledged Suio-ryu master. The normally stone-cold stoic Itto then promptly loses it and falls to the ground weeping. Daigoro cries with him; so do we.
For bonus points, Masatsune and his army go out of their way to avoid injuring Daigoro while doing everything they can to stop Itto.