Countless disturbing moments in anime. I see (at least) two of them mentioned here (The Griffith moment, and FMA's father of the year moment).

But I'd suggest being more positive and talking about the most satisfying moment instead, which also goes for Berserk when a certain chad slapped the fuck out of a certain bitch. It was the first and last time a Japanese manga/anime/vn made me jump off my chair like an idiot screaming "YESSSS, LET'S GO!!"... followed by "please be safe, please be safe, please be safe."

Which moment are you referring to in berserk? 

Have you not read the manga? I wouldn't want to spoil it because it's such an awesome moment.

I have read the manga. I collected like 30 something of them. I used to wait for the next book with high anticipation. I just don’t remember all that well. 

I don't know how to use spoiler tags here. Just Youtube "Berserk slap" and you'll get a few results.

I think I know what you are referring to now. Possibly. It looks like it happened later than what I read. That’s ok though, I can’t keep waiting for the conclusion to that story. I gave up on having closure years ago! Good to see that little bitch got slapped at least!

My apologies for spoiling it then. It remains my most satisfying moment in fiction, and also one of the greatest character glow ups in the history of the medium

I still haven't got over Kentaro Miura's untimely passing... Everytime I think of the series, I'm reminded that we will never see the developments and closure as intended by the legendary author... and it just hurts. But hey... maybe in heaven! :)