Negative prompts for anatomy etc. don't work. The problem is that it doesn't know what hands and other things are. It just sees a bag of pink or brown or whatever pixels. If it finds two together it might just join them up thinking they are all one thing. I'm sure you've seen a hand blending into the other arm or whatever. It has no concept of a "hand" or how many wriggly things it has attached or which is a right or left hand.
Also, depending how you write your prompt it might think something is important and try to make two or three of them.
Further, the model was trained on 512x512 images so anything larger can cause duplicates or a second attempt at the same image in another version in the same frame. The GUI from AUTOMATIC has a high-res fix that makes a small image and then upsizes and redetails it which definitely helps with this problem but still produces bad images fairly frequently.
Negative prompts are more for "artistic" choices than anatomical ones.