One particular scene stands out, both for its subtlety and utterly terrifying implications. When John is searching for his family about midway through the movie, he happens to look up at the night sky. It's filled with cometary fragments, and he can see them coming down one right after the other, lighting up red on the horizon. Everyone follows his gaze, and is stuck dumb by the sight. More frightening than any in-your-face CGI disaster porn could ever hope to be.
Another example would been when John and his family had finally arrived to the bunkers: When everyone is getting off the vans, a loud noise is heard and a woman points to the sky and mutters “Oh my god..” Sure enough, when John turns to look, Clarke is shown about to make impact. The sky is shown absolutely glowing with fire from the about-to-hit comet while everyone immediately scrambles to get inside and seal off the bunkers before the shockwave hits.
John breaks into a house and watches a news feed of footage of someone who unintentionally streamed their own death; while filming asteroids crashing down in the distance, he notices one in the sky that doesn't appear to be moving at all... until it starts getting larger and he realizes it's headed right for him.
