VANQUISH

Only on Act 5-1: Denoucement

For this specific achievement, miGu sama found a good strategy to get the job done:

Once the door opens to this area, rocket boost toward the left. There will be a bunker there with gatling guns. Equip frag grenades and throw one or two into the bunker to damage or even destroy the droids inside. There will be regular red droids and armored ones.

Once you open the door to the bunker, immediately trigger AR Mode as there will be an armored droid heading toward you. Depending on the success of your grenade toss, there might be two or three droids remaining. Destroy them quickly and equip your EMP grenades.

Toss an EMP grenade toward the Buzzard to stun it and then quickly man the gatling gun (NOTE: grab the one that is closer to the Buzzard). Shoot the Buzzard for roughly 4 to 5 seconds, let go of the gun and immediately aim and throw another EMP grenade at the Buzzard. After throwing, take control of the gatling gun once again and fire.

It will probably take a few EMPs to get the job done. If you do not use EMPs, the Buzzard will jump off the platform when its health is about 50%. If you do see the Buzzard jump, just Pause -> Checkpoint to restart at the beginning of that firefight, because the game will autosave as soon as the Buzzard hits the floor!

If you didn't manage to get in on your playthrough, you can always level select after having beat the game and can try again on the casual difficulty setting.