Violence is present throughout the movie, especially towards the last third of the movie when the violence gets especially graphic.
A woman's arm is severed by a closing door.
There are several creatures represented: One type is a human zombie-looking being that lumbers about and appears to crave flesh, another is a slime-covered being with several eyes, sharp teeth, a long wriggling tongue and sharp claws, and yet another is an animalistic creature with long, sharp teeth.
A man sees shimmering eyes in a dark tunnel, a creature lunges at him, presses him against a wall, takes a bite out of his neck and a slithering "tongue" tries to go into the man through the wound; other men with guns shoot the creature and the tongue.
A man is grabbed by the face from above, he is pulled up through the ceiling, held by the feet and swung back and forth slamming into walls, and a plasma gun is fired and makes a huge hole in the ceiling and wall and the man is thrown to the floor (we see him covered with rubble and he appears to be dead).
A man is grabbed by the head, swung back and forth slamming into walls, and dragged away by a creature.
A man is injected with something and we see the man snarl and writhe and begin to transform (his hands begin to enlarge and become snarled and he sprouts long nails).
A zombie eats a rat (we hear a crunch and see the tail wriggling between his teeth), and then picks up a knife and lunges toward two men holding guns, who shoot it.
A naked (see sex and nudity section) infected woman who is missing her left arm is using scissors covered in blood to write a message on the wall. She then proceeds to attack two of the Marines who are forced to shoot her. Her corpse is shown laying on the ground with several bullet holes in her chest, and her chest is covered in blood. (Unrated Version)