[Vader]

The alt ending is bad.

I don't necessarily agree. I never read the text the film is based on, but from the synopsis a friend gave me, the alternate ending comes much closer. The original story also centered around the last man on earth, and the "Dark Seekers" created by a plague. The man spent his days, not working towards a cure, but killing the Dark Seekers and throwing them into oil fires that were still going. At night, he would retreat to his fortress, and watch the Dark Seekers taunt him from outside. Needless to say, he was lonely, and the female Dark Seekers would try and entice him to come out. Finally, he encountered a woman during the day, and was so overjoyed that he invited her back to his compound for protection. Of course, she was a Dark Seeker, but mutated to be resistant to light. She let all of the others in, and they took the man back to their "hive", where he was put on trial for the murder of thousands of Dark Seekers. In the audience, there were women and children, the latter looking at him in terror while the mothers consoled them. He realizes that these people are not simply animals, but they have a culture, a society. At this moment, he remembered what his mother used to tell him that if he misbahaved, the "bogey" man would get him. Here, he was the "bogey man". So, the guy who we are rooting for the entire story really turns out to be the bad guy after all.

So, the alternate ending, while not completely true to the text, comes much closer to this realization, to me, at least.