Hmm a few things off the top of my head:
- promising fic with weak ending, maybe it fizzles out or ends abruptly or seems unresolved in a way that doesn't seem intentional
- frequent typos or misuse of words (you keep using that word, I do not think it means what you think it means)
- good story but some of the canon characters seem more like original characters wearing the canon character's clothes (I love a good OC but only if it's clear that they're an OC)