This is a very easy achievement. You can get it while you are in the factory. First you need the disc shooter, which is in the same room as the captive Agent HH. With this you can kill the guards very easily. All you have to do is hide, so they can't see you, and wait for the moment, when they turn their back to you. Now target the Tank and shoot. With this you can damage it, and the Alpha Guard is totally helpless. Get close to him and press the X-Button for some kicking and killing.
But be careful: Most of the time you will meet a pair of those soldiers. To kill both of them, you have to render one Guard helpless, hide and wait for the other to go to his partner. You have a few seconds, during which he will try to help his collegue. When you see his tank, target it with the disc shooter and then fire at will.