What is a monster? A monster can be almost any size or shape.
https://en.wikipedia.org/wiki/Monster#Etymology
Prophecy is a basic earth monster movie.
https://mondocoltd.wordpress.com/2019/05/19/prophecy-1979-the-original-screaming-bear
https://ew.com/movies/2018/02/25/annihilation-screaming-bear
Annihilation seems to be more of an ET monster story.
However, the ET entity is never shown in its original form, just how it can create various shapes and mimic things.
https://bloody-disgusting.com/movie/3500147/want-see-nightmarish-monster-bear-annihilation-glory
https://www.rogerebert.com/reviews/annihilation-2018
https://www.filmcomment.com/blog/deep-focus-annihilation