>Still arguing over Quilladin being Grass/Dark
Other than looks, what makes a Pokemon a Dark type is how they act. Even Absol regarding the lore that Absol is based on. Besides playing dirty and being sneaky, overly violent Pokemon are also classified as Dark.

Quilladin
> It is gentle and avoids battle.
Frogadier
> Frogadier attacks by launching small stones wrapped in bubbles at its opponents.
> It is better at jumping than Froakie, and jumps into trees during battle to confuse its opponents.

Of course, the final evos can be completely different but we'll all find out in October.