The part in which I have to defend Alyx while she's exposing core of the generator is way too hard for me. I can just reach the moment when the core is exposed, but there are way too many enemies to use the gravity gun safely.
What tactics could help me?
Will Combine soldiers spawn infinitely, or could I just kill all of them and then hit the core? Or, for that matter, are there any instances of enemies respawning over and over in HL2?
As I recall, there's several supply boxes in the center. I would save these until you need them, due to them trying to give you what you need. In my experience, the boxes are also weighted towards magnum ammo and crossbow bolts, so don't be afraid to use them.
My general strategy is as follows:
For the initial waves, stay near the electro-walls and kill the soldiers as they are dropped off, with grenades and the SMG. When the white soldiers start appearing, switch to the Combine rifle as they drop that ammo (use the Gravity Gun for easy ammo pickups).
As soldiers start to approach from both directions, move to the center and crouch behind the little wall for cover during reloads. There's going to be a lot of enemies, so I use the magnum and crossbow at this point.
When Alyx says the core is exposed, blast it with the Gravity Gun and sprint past the gate. I believe soldiers will continue to spawn until you make it past the gate. Yes, you'll probably still be shot, so hopefully you've done well enough or saved some supply boxes to have enough health/energy at that point.
There's a couple instances of infinite enemies like this, or overwhelming. Usually they are pushing you to run/escape somewhere.
There are some turbines in a container. Go near that container and press E. It will open it. Now go near a turbine and press E. Freeman will pick up the turbine. To set it up, go anywhere and drop it. Now it will automatically kill soldiers that are coming to kill you. Sometimes soldiers shoot the turbines and they fall. To set it up again, go near it and press E. He will pick it up. Then again press E. You will found more information here : http://googleweblight.com/?lite_url=http://www.visualwalkthroughs.com/halflife2/anticitizenone2/anticitizenone2.htm&ei=rIocQMny&lc=en-IN&s=1&m=765&host=www.google.co.in&ts=1463473702&sig=APY536xa0MwzkhREBpzsxhkUH58hXzKnIQ
Prepare, fight the good fight, then cut and run.
Pre-open the supply crates, throwing them with the gravity gun so they break open and spill their contents without you necessarily picking them up. (nothing more frustrating than picking up a 45-shot ammo box and only getting 3 bullets out of it).
Set all the hopper mines you can find to guard the usual enemy hang-out points.
Then, work briskly between the two entry areas. Early on, before you're too badly mobbed, try to kill them on your side of the force field, so you can pick up their ammo without having to switch to the gravity gun. That won't be practical as the pace picks up.
Listen for Alyx's progress and as soon as it's possible, go blow the energy ball out of the generator and instantly run like the wind for the doorway Alyx just opened behind it. Seek cover, e.g. in that small control room on the left. Alyx will promptly close the door.
Taking a beating is hard to avoid. If you're hurt bad, choose carefully where to jump down to minimize fall damage. The next few areas won't contain much in the way of enemies, but have a goodly amount of supplies if you search. Look behind plain boxes (including on high shelves) and also catch the Lambda cache at the bottom of the damaged stairwell at the bottomless pit.
If that's not enough, fight carefully through the zombie-headcrab area that's next, making full use of the barnacles to kill enemies for you. The area with a poison zombie has two Lambda caches, so take the time to kill the black crabs and zombie, then explore.
