There seems to be a bit confusion regarding this, so I'll clearly outline everything:
First off you'll need the DLC entitled 'The Cerberus Network'. You will receive a card with a code for this after buying ME2 new. Type the code into EA.com and the next time you log in to ME2 you'll have the option to download 'Zaeed's mission'. If you have no code you will have to download it from the Game Marketplace for free.
Downloading this will add Zaeed's location to the Galaxy map, also adding 'Project Firewalker' and 'Normandy Crash Site' missions, along with the powerful shotgun the M22a, a new lightning Heavy Weapon, and a decent but non-customisable Cerberus Armour. The latter are irrelevant to this or any achievements.
Go to the Galaxy map, navigate to the 'Omega System' and find 'Gain the veterans loyalty'. Dock into the Omega station and approach the first guy you see in Omega, Zaeed.
Now as long as you gain Zaeed's loyalty the achievement will pop. He wants revenge so doing his mission Renegade style won't require high renegade, it just requires you choose all the renegade options. You will encounter more hostiles and receive less rewards for Renegade.
You can however do this Paragon style (for extra resources and rewards), you can save the workers but you'll have to have at least a 30%+ Paragon to convince Zaeed you did the right thing and gain his Loyalty.
Once you complete Zaeed's mission the achievement will unlock.
*'Remember do this Renegade if your Paragon is low, and do it Paragon if it's high for better rewards'.