My first impressions from this movie is that it should have been split up into a short OVA miniseries rather than one 2-hour movie, as the pacing made it hard to hold my attention. However, Hells still had aspects about it that made it enjoyable.
The first thing you'll notice is the striking art style. I loved the gothic flair, sketchy outlines, and very over-the-top exaggerated animation. It captures the style of the manga well, and each colour choice is exceptional. Rinne's brighter palette really stood out against the dark, moody atmosphere and more muted tones on the other character designs. I appreciated the subtle visual cues, such as stitching appearing to be wherever Steela was.
Another aspect I enjoyed about this film was that it felt very hopeful. Rinne is a very likable protagonist, while also eventually learning to stand up for herself and what she believes in. Her friendship with Steela was so sweet, and the way she gradually won over the others was enjoyable. She very much is a "power of friendship" type protagonist and even reminds me a little of Suzuki Iruma, but that's exactly what I liked so much about her.
This film is free on retrocrush if you want to try and give it a chance.