- The scene where Marty almost fades from existence. Seriously, just imagine what it would feel like to see your own hand fade away and realize that this is the end. And since you're being erased from existence, not killed, that means if there is an afterlife, you're not going to it, because your consciousness and all your memories will be non-existent. note The tense music in that scene really does help to sell the horror of it all.
- Bad enough that you fade completely away from time and memory, the fact that you go through the worst pain you've ever felt in your life adds to it.
- It can't be easy trying to accomplish a seemingly impossible task in a few days knowing that if you fail, you will be utterly erased from existence. It's a wonder Marty managed to keep a pretty level head with the knowledge he was, er, desperately racing against time.
- Biff attempting to rape Lorraine in the car. This scene is especially unsettling for women who have been raped themselves or greatly fear it happening; that you are completely helpless and all you can do is scream and cry for help. What sells it is Lorraine having a tear-soaked face as she looks up with fear to George and quietly says "George, help me, please." Which makes the outcome really satisfying and heartwarming.
- Surprisingly dark and frightening, given the overall light, comedic tone of the rest of the movie. And poor Lorraine, with the only person to save her the perennial wimp George, who (as the earlier scene in the cafe, when Marty gets George to talk to her about "density" shows) she wasn't even really aware of until a day or so ago. George could just as easily have caved to Biff, closed the car door, walked away, and left Lorraine to be raped. Which makes George standing up to Biff all the more epic, and turns "No, Biff. You leave her alone," into one of the greatest Moment of Awesome Pre-Asskicking One-Liner ever. And adding extra octane to the Nightmare Fuel, the whole reason Lorraine is in that situation is because of Marty! Marty antagonized Biff and took Lorraine to the dance, where Biff found them both and drunkenly decided to get revenge. If Lorraine had gone with George as originally intended, Biff might not even have seen them!
- Marty watching Doc Brown get shot. Twice. He's seventeen and he watches his best friend get shot. Then he tries to prevent it, and arrives just in time to watch him get shot AGAIN, and feel like there's nothing, ever, he can do about it.
Doc Brown: Oh my God. They found me. I don't know how, but they found me.
- Then there's Doc's reaction when he sees the terrorists coming, and everyone knows shit is about to hit the fan.
- Doc gets to witness his fate in 1985-A firsthand. He wasn't just locked up in a mental institution per Part II; he was also lobotomized. It does a lot to explain why he was so eager to abandon science altogether and settle down in the less-advanced society of 1885 in Part III.
- The idea that he might fade away for real when the Lone Pines timeline reasserts itself is literal nightmare fuel for Marty, who dreams that Lone Pines Marty comes back to watch it happen. Worse, Doc takes his side, with a dialogue authentic enough to easily serve as the happy ending of a story about Lone Pines Marty. There's something uniquely chilling about getting a first-person perspective on the stock evil clone scenarioparticularly since Lone Pines Marty is as conscience-stricken as you'd expect the Marty we know to be in the same situation.Marty: Doc, you gotta help me! Help explain[Doc walks through Marty's fading form]Doc: (addressing Lone Pines Marty) Marty, my boyit's good to have you back.Lone Pines Marty: You too, Doc. He's just gonna vanish?Doc: That's the theory. Let's see how it plays out.Lone Pines Marty: You know, mad as I am...I'm sorta sorry to see him go.Marty: No, no...Lone Pines Marty: Sure, he tried to take over my life and all, but...Doc: He's not real, Marty. He's just an aberration. A bubble in the time stream. And it's time for that bubble to...Marty: POP!