Tim's suicide attempt and everything that follows, including Gail's rant to a nurse who won't let her in to see her.
Grant dying. Just when everything was coming together, too...
Everyone's reactions make it worse. Irene notes her sister was the same age when she died. Eric is the one to find the body, and Gail's there, too.
Jackson attempting to deal with the death, but his two best friends are absolutely no help. (Though to Henry's credit, he tries. Terrence, on the other hand, doesn't try at all.)
The tornado. The sheer thought of such a small town being savaged by a natural disaster is saddening, but what makes it worse is that the farm Gail and Hank live on is completely demolished and Hank vanishes, most likely killed by the tornado.
Gail finding her dog curled up under the collapsed porch with a broken paw was rather sad, too.
Oh, and the worst part? Hank didn't die in the tornado. That's right, he survived. He ended up being found miles outside of Pageson, comatose and with his face so bashed up, no one can identify him. Things seem to get better, when Gail ends up at that same hospital (long story), and her presence seems to wake Hank up. Happy tears at first, as it seems like everything will work out after all... And then he dies for real, right in front of Gail. To say the authors decided to Yank the Dog's Chain is a massive understatement.
Colleen dying of Parkinson's, poor girl.
The first part of Emily's reaction para is pretty sad, too. Even the title, which is a lyric from Wicked: "The Wicked Cry Alone."
The entire thing happening right on the heels of Hank's supposed death makes it worse for Gail, who, as The Reliable One, is asked to tell the other teens what happened. She comes through, and it leads to a bit of growth in her character (managing to truly empathize with Henry, considering becoming a hospital chaplain instead of an actress, etc.), one has to imagine it wasn't easy for her.
And when Hank dies for real, Gail doesn't tell anyone because she feels like everyone is already underneath a lot of stress and don't need to hear about her problems.