It comes down to two characters, although one of them is canonically dead at this point in the series (even though I've drawn her a crap ton)
First up is Vicky, one of the main characters and she is one of my favorite characters to draw, I think it comes to down to hair, fur color and musculature that does it for me. I've had some people admit they find her attractive so I definitely struck the sweet spot with this character XD
Next up is Julia, my main character's mother. She's currently dead in the series like I said but she is one of my favorite characters to draw and imo, the most attractive. And its because of.....well I'll just show you: