Ace Combat: Assault Horizon

You just need to kill 10 enemies through a dog fight. The CPU count for this achievement so you can set up a private deathmatch or whatever with a buddy and get this quickly.

Use a fighter and engage other aircraft. Use multi anti air missiles, launch some off so that you only have to finish off the enemy planes with your cannon or a critical missile shot. Destroy air enemies in a dogfight (where you press both shoulder bottons whith the circle around the enemy). Just do what you would normally do in the campaign. If enemy plane is damaged it is quick and sometimes you can automatically be in another dogfight. rinse and repeat.