Every last second of E.T.'s Disney Death. The scene of him dying on the table, while Elliott stretches out his hand and tearfully begs him to stay with him, is just heartbreaking. There's also the fact that as he's dying, Elliott is getting better. Just think how guilty Elliott would have felt if E.T. had actually died...
When the scientists are trying to give CPR to E.T. All you want to do is jump in the TV and push them away. Spielberg deliberately filmed the scene so it looks like they're hurting ET rather than trying to save him, since that's what any kid like Elliot would naturally think. Then there's Elliott screaming for the scientists to leave E.T. alone... then just crying when it looks like he's actually dead...
In addition, the single shot of Gertie jolting and then crying as she watches the scientists defibrillate E.T. is probably one of the biggest Gut Punches in cinematic history.
Michael, a mature teenager, curling up among the stuffed animals in the closet to cope with his overwhelming concern for his younger brother. But then he sees the flower E.T. revived dying and then realizes what's happening.
"Look at what they've done to you. I'm so sorry. You must be dead... because... I don't know how to feel. I can't feel anything anymore. You've gone someplace else now. I'll believe in you all my life. Every day. E.T... I love you."
The ending, as E.T., about to depart, says goodbye to Elliot.
If you're not already sobbing the moment Elliott steps up to E.T. and John Williams' music swells up, the long goodbye hug E.T. gives Elliott will seal the deal.
And the way they both say "Ouch".
And how E.T. asks Elliott to come with him.
Not to mention the reactions of Gertie, Michael, and even Mary to all of this.