Malignant is an amazing film and its villain fits it perfectly. One of the main themes of the film is a woman's right to bodily autonomy. This theme is shown by the fact Madison "Maddy" Mitchell's fight with Gabriel is to protect her own freedom.
To me Gabriel isn't one of the best villains because he's scary, but because he's a little more complicated to me. Though I'm not going to argue that he should have won at the end of the movie.
If you haven't yet seen the film I would highly suggest watching it before continuing to read this post.