This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Pretty Guardian Sailor Moon
Rei crying out for Minako's death, kneeling down and shouting to the sky in tears after focusing her grief into rage to destroy a youma.
The scene where the others read Minako's goodbye letter. Made only sadder by the ost, Sayonara-Sweet Days AKA Minako's own funeral song.
In the final act, as the Dark Kingdom crumbles apart all around them, Jadeite refuses to leave Queen Beryl's side. Beryl, tired of keeping up illusions, removes the spell she cast on him to compel his loyalty so that he will leave. But Jadeite doesn't leave, his loyalty to her is real and has been all along, and then they reach out to one another before they are both crushed by the rubble of the collapsing palace.