The only werewolves I can think of are, unfortunately, all characters who probably won't be coming to Smash.
We have Wolf Link, who I'm not sure counts as a werewolf because he just turns into a wolf and not the beast typically associated with werewolves. He probably has the best shot of any of the characters here, if only because he could be added with Midna as a duo character ala Duck Hunt. But, even though Midna is my favorite LoZ character and I want her playable, the unfortunate truth is that the ship has sailed as far as that goes.
The Werehog would be weird to implement, since it's a transformation of Sonic. You'd either add him to Sonic's kit, which wouldn't make sense because Sonic isn't known for transforming into the Werehog on a regular basis (and freed himself from the curse by the end of Unleashed). Or, you add him as a standalone, which makes more sense now that Shiek and ZSS are no longer transformations, come to think of it. While I'd love playing as stretchy-arms brawler Sonic in Smash, there are a lot of characters from the Sonic franchise who should get in over the werehog. If we want to make a character who plays kinda like Sonic but is more about brute strength, knock knock it's Knuckles!
The Castlevania series has
Cornell. He's not very popular, since Curse of Darkness is not that well-liked among Castlevania fans. Alucard, Trevor, Soma Cruz, and possibly Dracula (though I do think the boss role is a good fit for him) spring to mind as characters who should be added before Cornell. Miriam also springs to mind. Bloodstained may be a spiritual successor to Castlevania, but that just sorta makes her feel like an honorary Castlevania character. And technically being from a new franchise would be all the more reason to add her.
Digimon has Weregarurumon. One of my favorites, but we'd likely get Agumon first. And if we got Gabumon, it's a toss-up whether Weregarurumon would come into play in his kit or not.
Lastly, there's
Jon Talbain from Darkstalkers. I don't know much about the popularity of Darkstalkers characters, but of course, we all know Morrigan is the face of the franchise. Maybe they'd choose Jon if a Morrigan with covered-up cleavage isn't something they could add? I used to think this was possible for Morrigan, but the whole Mai thing has me very unsure. Regardless, if they go for a Darkstalkers rep who isn't Morrigan, it wouldn't necessarily be Jon.
So yeah, us werewolf fans will probably have to stick to playing as Wolf for the time being, though that's not so bad