Okay, first off, 4chan's definition of "edgy" is complete bullshit, and it's really just a buzzword now. Edgy actually means innovative or a little racy, something new that might be pushing certain boundaries. I assume the source of the word here comes from "cutting-edge", which essentially means the same thing as edgy, but sounds emo or something.
And what a lot of people don't understand is that some designs are supposed to be 'edgy', using the 4chan version of the word. Yveltal represents death and the end of life, so it rightfully looks dark and sinister. The same thing can be said about Houndoom, Mandibuzz, and plenty of other pokemon. It just fits their flavor.
I think the main issue here is that you just can't please anybody with everything. Cute pokemon are declared to be childish cuteshit, while anything with a sinister theme, dark demeanor, or fitting color scheme has the word 'edgy' thrown at it six ways til Sunday. It's all really just a bunch of bullshit, to be honest.
