Obtain 12 000 points in the Kunlun Mountains mission in the Campaign.

Difficulty makes no difference to this achievement so there is no point in making it harder for yourself.

Headshots give a 25 point bonus
Adrenaline kills give a 50 point bonus
Multi-kills give a 100 point bonus

I would recommend using a steady AR/LMG, with your main gun being a sniper rifle. Every kill you go for, aim for the head with a sniper rifle, and chain them together as fast as you can for bonuses. If you reach a section where enemies appear and its a programmed route, restart checkpoint and utilise claymores for big points.

If you need any help feel free to PM me.