I play this game with the extreme content filter on because of the language and violence. Even with the filter the language still surprised me with plenty of words like sh*t, b*tch, and some more milder profanities. Some of these words are in the script during story development and some are during the actual gameplay. You hear the phrase "Eat sh*t and die!" multiple times throughout the games as NPC's kill enemies. Without the filter it is much worse.
The filter does however take out much of the harsher violence. Without the filter you can literaly blow enemies apart with the shotgun or saw them in half with the cainsaw bayonet. All of the violence is extremely bloody often spraying up onto the screen. WITH the filter there is no blood and enemies do not fall apart. The screen still tints red when you are shot but it is not gruesome. Some of the environments can be a little disturbing with or without the filter. Some areas depict the after math of human encounters with aliens. Bodies are strewn about often in very bad shape (dismembered, bloodied, slightly decayed, etc...) However, none of it is very bad if you don't look closely at it.
The strong point of this game is playing through the story mode with another player. The level of cooperation needed is incredible. My brother and I spend a lot of time playing this game together. It's a fun way to spend time with a good friend or family member.
In the end, this is a great game; great controls, graphics, gameplay and co-op. It is dark and violent but this can mostly be avoided with the filter. It is however, still a game about war so it is best for more mature gamers