It's considered one of the worst anime movie adaptations of all time, to the point that Devilman fans actually have a day to 'mourn' the film's (original Japanese) release every year, that's how bad it is. (https://soranews24.com/2016/10/11/movie-fans-pay-respects-on-the-12-year-memorial-service-of-the-live-action-devilman-film/)

Apart from that, it's a terrible film in general; plot points are constantly dropped and skipped over without warning, the special effects are hot trash, and the English dub is way over the top. Not to mention this film is completely batshit insane, especially if you take a lot of the scenes out of context:
https://www.youtube.com/watch?v=HWrxD17yM0U
https://www.youtube.com/watch?v=CYucts5lWEQ
https://www.youtube.com/watch?v=0XaiIW8WPyE