My girl "TRIBBY". She's all you need in your life ?
Tough one, yet easy, as the stories I'm most pleased with have female leads rather than make leads.
I could say "A Wolf In the Night" has the most developed 'heroine.' And that character was the most exhausting to write at the time. I had to research a lot for it.
But.. my favorite is from "A Scarred Wonderland." I still dunno where that story came from, but that character... eats at you. Or me. I can't really even reread it to make minor tinkerings I considered because I didn't want to jump back into her head. And if you pay enough attention, you'll realize this character appears in one of my other stories. Only... far darker.