Well, at the end of the first series when Ami, Rei, Minako and Makoto died. In Sailor Moon R when Mamoru broke up with Usagi. The end of Sailor Stars where pretty much everyone died... The scene in the Sailor Moon S movie where Luna was crying because she was in love with a human but couldn't help him because she was just a cat. And the scenes in the cathedral with Haruka and Michiru. Especially Michiru getting shot up.