In Half-Life 2: Episode One, the last underground level is where Gordon and Alyx find an unpowered elevator, look around for a switch to power it on, and then try to survive the zombie onslaught while waiting the elevator to arrive.
In my previous playthroughs, I always struggled on this part, and could only survive after a few tries. (Damn you, massive zombie horde! Damn you, zombies carrying a grenade! Damn you, slow elevator that takes forever! Damn you, flashlight that doesn't have enough battery!)
Now that achievements were added to the PC version, I'm replaying this game, and I thought about The One Free Bullet achievement:
Finish the game firing exactly one bullet. Grenade, crowbar, rocket, and Gravity Gun kills are okay!
I tried getting it, but I'm repeatedly failing in this level. If using shotgun and sub-machine gun against a massive number of zombies in the dark was quite difficult, not using these weapons seems impossible! Half of the time I die, and half of the time Alyx dies. (Before trying to get this achievement, I didn't even know that she could die!)
So... What are the suggestions to pass this map? How to survive long enough? How to get this achievement?