There is much more violence than the first two films and could be considered intense for toddlers to children of age 5. A few characters are killed (one onscreen, no gore whatsoever), and one character attempts to kill another, almost succeeding. All the above may be found intense.
Also, the introduction scene is purposely very frightening. There are many closeups of buzzsaw-like spider jaws, and one of said spiders howls in a very creepy tone.
One of the villains refers to the dead bodies of the heroes a handful of times.
In addition to the increased amount of violence, this film is also significantly darker in atmosphere and themes than the first two films. One of the heroes is "seduced" into turning against and hunting down his allies (in a similar vein to Star Wars: Episode III). It is frequently suggested throughout the film that there is an animalistic side to everyone waiting to take over that is devoid of any morals or positive emotions; this idea may be frightening to younger children.