You've obviously gone in for good equipment: an 85mm f/1.2 is not economy gear. At this level, there aren't too many technical questions apart from "am I using it right?"
The more techie people have talked about exposure, and I'll accept what they say unreservedly!
It's also true that the model is looking rather soulful. This could be a fault (and you seem to think it so - did you not get a big variety of shots?)
My initial comment was going to be that it's a very central composition. That's a novice error - put the subject in the middle. However, your portfolio shows that you are an experienced and competent tog (good thing too, with that outfit!)
Putting the expression and the composition together makes it a very formal picture. Assuming - and it's a reasonable assumption, from looking at your other shots - that it's all intentional, the composition is a way of isolating the model, putting her out on her own, unsure of her own status and beauty...
In those terms, this is a resounding success - and the slight underexposure is not an issue. Except... Maybe a little light on the right hand side, to separate the model's head from the dark background.
Or, maybe, that, also, is intentional. She fades into darkness?