The opening credits alone are incredibly chilling. After Ana crashes her car, we cut to scenes of societal collapse and the chaos that reigns as the undead overrun cities within the span of only a day. The black background of the credits sequence with the red, animated, bleeding text that sweeps across desolate pitch dark canvas is probably more spine tingling than most of the gorn that ensues throughout the rest of the film. All this playing to Johnny Cash's grim rendition of his already solemnly apocalyptic "The Man Comes Around".
It's worse when you find out that most of the scenes of society coming unglued are actually archival news footage. Yes, including the out of control dump truck.
Add that the final part of the opening credits shows zombies attacking a news crew before intersplicing with static and black screens and the ending with the chilling final line of Cash's song, taken directly from the Book of Revelation:
And I heard a voice in the midst of the four beasts
And I looked, and behold a pale horse
And his name that sat on him was death, and hell followed with him
A particularly effective bit:
"You're going to kill my family?"
Note that his "family" was Luda and her unborn child, who were infected and now undead.
The sheer fact that he goes briefly Ax-Crazy due to it just hammers it in. He's on the run from the dead, his wife and child are now dead, and his friends and family are probably either being fed on or are a part of the hordes. He's lost pretty much everything. No wonder he snapped.
The zombified baby itself.
If you listen closely before it is killed, you can vaguely hear it speaking one word through the incoherent guttural screeching.
The early scene where Ana and Luis wake up to be attacked by the zombified neighbor girl. Not specifically for fear of zombies, but it makes you realize that whenever you go to sleep you never really know what the world might be like when you wake up.
Michael walking into the sports department, looking for a better weapon, and coming across a turned over bucket and mop in the middle of the silent shop. His face when slowly reaching for the first best weapon within his reach mirrors the horror of the situation perfectly.
The overhead view of the suburbs as Ana is driving out just simply gives a better view of how much the shit is hitting the fan.
The zombies in this movie. It's one thing being chased by mindless, rotting, walking corpses, but it's even worse when those corpses are also screaming maniacs that sprint towards you in an utterly terrifying Unstoppable Rage.
It's far worse than that. It's not outright stated, but various scenes in the movie indicate or at least strongly imply they're intelligent to some degree.
In the bonus feature, "We Interrupt This Program", a continuous news broadcast that shows the world descending into chaos in just over a day:
19 hours into the outbreak, Los Angeles is completely overrun, and the United States declares martial law and seals off its borders.
20 hours into the outbreak, 10 million are estimated dead in the United States. This was deemed by the anchorman as a very minor estimate, and didn't know where to begin guessing what the cumulative global fatalities were.
26 hours into the outbreak, there is a thermonuclear exchange between Russia and China.
There's a fair bit of Nothing Is Scarier in this movie, and we see plenty of abandoned scenery and discarded items that will most likely never be touched again, particularly children's toys and bicycles. And some of the children’s toys and bicycles have blood on them.
A minor one, but early on, as Kenneth is initially walking past Andre, Luda and Michael, the latter repeatedly tells him "You do NOT want to go that way." When Ana asks what is that way, he only replies that it's "pretty bad." Then Andre reveals that the road is thick with undead, and they had just tried to get through. When there were eight of them, according to Michael. One can easily imagine what happened to the other five.
