For me, Pangoro, with Noivern coming in a close second. Maybe it's my Dark-type bias that makes me love Pangoro so much, but I really like its design, and after using one in this run, I've grown to respect it as an absolute powerhouse. My Pandora was good for basically every situation. Nothing fazes her. In fact, Pangoro would probably be my favourite Pokemon overall if not for Simisear (yes, I do actually like it) and Hydreigon.
As for Noivern- well, that's just pure bias. I love wyverns, so naturally, I'd love the Pokemon that's outright based on them.
I actually have newfound respect for Sylveon, too. I tend to rather reset Fairy-types, but my Sylveon in this run, Azriel, actually made me really enjoy using one. I mean, sure, I'd still call Fairy one of my least favourite types purely because the designs of a lot of its Pokemon (it's not just them- Poison's actually gone down in my list of favourites because I don't care for a lot of the Pokemon in the type), but because of Azriel, I'm actually really looking forward to using more. So I'd say Sylveon's a favourite for that reason alone- making me respect a type I once resented.