A significant amount of strong violence. Bodies (fully armored) of dead space marines are found desecrated and strewn about in a variety of ways.
Space marines use guns and chainsaw swords to kill enemies causing large amounts of blood to spray, however in most combat scenes the camera is positioned so that the most gruesome moments are out of frame.
A space marine is killed and falls over, revealing that a monster has ripped a chunk out from the back of his head. Blood pours out of his head.
The violence is the film is strong and bloody, but the film's poor (blocky) graphics often make it seem significantly less gory/intense than it otherwise would be.