Call of Duty: Black Ops is a military first-person-shooter, and the average level of violence in multiplayer and campaign slightly greater than most first person shooters. While there is no explicit gore in multiplayer (just blood), the level of violence in the campaign can get quite strong and graphic.
The downside to the game is that it is realistic, therefore you see blood, violence and other negative stimulants that can be harmful for a child. In order to win the game, you need to win the war. Since the video game is about war, you have to kill as many people as possible.
