KD ratio makes a relation between how often the player dies compared to how many enemies they kill. A good KD ratio average is around 2:00 implying that the player has taken down twice as many enemies as they have been killed. Most casual players have and maintain a KD of around 1:00.
The best Assault Rifle in Modern Warfare 2 is the Kastov-74U, an extremely powerful rifle that combines best-in-class stopping power with high mobility.