Ok I spent 6.5 hours on this guy here's is the intel you'll need in kicking his butt hope it helps.
At the beginning run towards him but not close use the assault riffle (Terralite III best assault riffle there) and keep scoping in and out while shooting (quick Scoping) very effective if you can pull it off then he'll jump down stairs you can continue to quick scope him or get into cover then continue with quick scoping. If done really well he should have called for back up as soon as that happens run outside from the direction he came from in the beginning upstairs and defeat any henchmen around.
Now you're going to stay up there with your back to the wall in the corner by the spawn door aim at door you just came out of and pull out your shotgun. You'll need to watch your mini map and reticule as soon as they are coming through the door or your reticule goes red shoot it a one hit kill most of the time you might need to quick scope from time to time (FYI quick scope with a shot gun can be slow).
006 will start this funny running pattern where he'll run round to you (might have to move to the right to see him) stands then jumps down stairs (while he standing he's actually aiming at you. You have two choices you can (a) shot him once with shot gun and move back into the corner and he'll leave or (b) you can quickly change to the assault riffle and quick scope him. He will do this for a while then stop and hide most of the time upstairs on the opposite side, when that happens as soon as you get the chance lean against the wall put in a couple of shots into him and he'll start moving again. If this done successfully done two to three times the spawn door where you standing by will open you can go in there and defend yourself good luck as I had bad luck and he would stop running around so I had to leave the room.
Now if you were like me and had no luck hiding in the spawn room when 006 is by himself the third time his pattern might changed so you will need to adapt to how it works quick scope and cover is still the best option in the same area you are in (that's upstairs on the right hand side). He will say "I need a helicopter kill him use rockets if you have to", as soon as you hear that if you're out side run inside as the chopper is out and you're near the end of the battle. If you were upstairs good if you weren't can't help you sorry.
Run through the first door (opening) and take cover by the fully covered metal railings and squat, breathe and don't rush quick scope anyone close who is upstairs don't bother trying to shoot anyone downstairs you'll waste health and might die. Quick scope and cover until Alec (006) is beaten. Now don't start running round the room like you won the World Cup or UEFA Champions League as you still need to get to the elevator so stay in cover clear any remaining henchmen, once done jump over the cover to the floor below and run up the stairs to the left and get in the elevator and press X on the button as quickly as possible. The reason for all this is because the helicopter is still there trying to shoot you and as soon as you leave cover more henchmen spawn to kill you.
Well that's all the knowledge I can pass on for now Good Luck 007
PS: when run low on ammo the move forward close to the door where you killed all the henchmen and collect ammo. The Terralite III is carried by some of the henchmen
Also from time to time the henchmen will flush you out of cover with grenades I shouldn't need to say it but just in case RUN!!! just don't jump downstairs.
Also I mention the third time this is when you kill all his henchmen and you're one on one with him.