Weird. I was about to post on the greatest movie ever thread then I saw this one. My favourite movie of all time. Ending made me cry even though I had read the book and still gives me a lump in my throat to this day. I have the SE DVD and when you take the disc out you see a pic of Chief picking that "Thing" up at the end, which I think could ruin the movie for someone who hasn't seen it before, like the cover of the original Planet Of The Apes.
I don't think Ratched/Ratchet (never quite sure) is evil, she just does her job with an over-abundance of zeal, reminiscent of a witch hunter. For the purposes of the movie however, she is the evil character.