Diablo – What determines low health for the Survivor achievement

Just for the record here is how I did it. It might not be easy, but it doesn't rely on luck.

Start a second level of an easy difficulty single-player campaign. I picked the mall for this. Before exiting safehouse kick all the bots from the game (they would shoot and kill the charger). Now get in a large open area and clear it of all the zombies so that you have a lot of space to run around. When the charger spawns, always keep your distance from him (so that you have lots of time to sidestep his charge) and shoot him a good deal (melee attack do 500 damage, charger has 600 health, but the actual damage done imho depends on how far your target is, meaning that especially in this case it will be much smaller). When he charges, get some distance from his path, then try to run towards him. Try to time it so that you "hit" his shoulder as he passes you by.

If it doesn't work, just run around and wait until he charges again. If he gets too close to you, just run and try to jump over a small obstacle, you can do that faster than him. Next time he misses his charge, you will get a nice distance from him. Most of all this approach requires patience as you probably will have to learn some of the game mechanics in detail before you succeed. But I find it much more satisfying this way.

It seems like you just have to survive three waves when the van is hanging, without shooting the wires that hold it up. The van will drop without you having to do anything.

This video might also be helpful: