This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Space Battleship Yamato 2199
Erich Domel's death, motivated by his will to not make his men's deaths senseless. The Yamato surviving, thus making everything a Senseless Sacrifice, only makes it worse.
"A Clockwork Prisoner": Analyzer re-activates a Garmillan android soldier in order to study it. He ends up befriending the curios automata, which he names "Alter". Later, Alter curiously peeks into the mainframe of the Yamato and finds a "goddess" (who is actually Yurisha) and goes to any length to pursue it. To protect the Yamato from a hack attack, Analyzer is forced to put Alter down. The episode, as a whole, goes to great lengths to explore the question of What Measure Is a Non-Human?.