The Thing's capabilities are far too inconsistent.

I don't hate this movie, but it bothered me how the Thing was entirely inconsistent regarding its capabilities. In a few scenes it is shown to be able to lance people with a quick tendril shot, or is able to consciously detach a part of itself. However, when female-Thing lured Kate into the room it clumsily chased her around when it should have been able to quickly kill her. Similarly, Dr. Halvorson-Thing was incapable of getting to Kate when she was "out of reach" during their showdown in the alien spacecraft when it could have simply detached a part of itself.

At least the Carpenter-Thing was more mysterious and seemed to not be quite so deadly as to quickly kill someone from 20 feet away with a tendril.