The alst boss for Unreal right? It wasn't that big and it did move about. The latter was what freaked me out. I think it would have been better in Half-Life if the last boss was something like the Gonarch (bigmomma). Things like that make it seem more like there's "no escape". On the other hand, with the Nihilanth, while it had that "wow" factor for being so huge, was quite easy to avoid by hiding behind the rocks.