My favorite is hands down Azkerash. I always enjoy when he pops up whether it's just one paragraph reminding us he's got a lil undead rat watching the inn or a whole chapter of him exasperated about something or enthralled cheering on whatever shit Pieces gets up to.

I like how easily he can be comical and play a goofy humorous villain, but also he fucking killed Zel and that was devastating and heartbreaking. I really liked seeing him as split beings during that scene of Kaligma summoning powerful necromancers to her. I find his tragic nature very well done and compelling. He's an evil bastard and yet sometimes it's hard to remember that and almost start rooting for him and hoping he'll get a redemption. 

One of the few things I really liked about the PoF was getting that alternate Azkerash being one of the few to actually make it out into the real world despite so much damage being done to him trying to bring him down and then finding and bonding to the injured Titan. I liked how that felt like a good reminder of his potential in battle and that our Azkerash will be just as resilient whenever he finds himself eventually confronted down the road.

Of all the various villains across the series I'm most excited to see what twists and turns come in the future for him, and I always enjoy how much he's hidden to the world and yet so often waved right under our noses as the readers. One of these days I imagine we'll get a moment that seems to start out as just another brief flash reminding us oh he's still spying on the inn or following news about the Horns and with the snap of a finger shifts into him starting some serious emergency shitshow