I almost- if not- always wind up crafting the story first and then flesh the characters out within the narrative. I could see where crafting maybe just 1 or 2 important characters first and then writing a story around them could work... but my brain just doesn't work that way.
This can lead me into traps occasionally though. I had a story idea that I was working on briefly a few months ago before re-shelving for a while because I had the story premise all worked out, and even several minor characters... But then I was having a lot of trouble trying to lock down what i wanted the MC to be like. Which is, like, obviously really important before starting a comic LOL I wasn't sure of her personality or talents, which led to difficulty in even locking down her design. So, like, yeah, that story is just in limbo until I manage to work that out.