Oh, I forgot to say mine. LOL.
I guess I'd have to go with Angelique Pettyjohn--she wasn't hired for her acting.
...then that kind of gives her an excuse, since she served her purpose.
But in response to your topic: I cannot think of anyone bad enough to--err--stink up the joint, but I agree with AtoZ about Ed McCready as Dr. Carter. McCready's UUHHHEEEHEHHAAAHH death cry could have hurt the scene, if not for the principals giving such serious performances.