Saddest episodes?

The only sad think related with Matt is that he never suffer for a painful death

Nanette Babcock wasn't a sad episode to me. I don't respond well to self indulgent victimization of characters, so that people like them, would relate.
To me, a 36 year old woman, commiting suicide, with her lover by her side. Because her cancer is winning. Is sad. A man who was abused as a child (even though he turned into a real dirtbag), is sad. Seeing said dirtbag, treating women who loves him, like crap. Including a vulnerable one and a blind one, is pretty sad too. Hell, even the transegenders storylines, in this show were sad. Because of how, lonely and misunderstood they were.
But a psycho bitch, who can't cope with her *beep* and finds herself excuses all the time. And decides to blow her brains out, because she will never be something she, either way, could never be. Is just pathetic.
And if you really hate one of these characters, to wish his death. Then you should wish for a mass suicide. Because they were all pretty despicable people, overall.