This is very nice, I'm not good with X and Y Poke'mon so I don't know what Poke'mon this is but it's very cute. I love the shading and lighting it's amazing ( the lighting must have taken hours! ) I have to say some things I really liked was, The eyes, the head and the backround. let's talk about the backround here, it's amazing and looks very nice here. All in all the picture is very nice and will have tons favs I can tell you that, so here comes the rating (pray I don't mess up here and over rate or under rate xD) I say (drum roll?) 4 and a half stars
okay, this is just adorable. I love how you drew the eye and the horns. how you did the colors on the horns is so pretty~ x3 (they look like they're glowing, too ) I haven't seen many pictures of chibi Xerneas, but the looking up at a star thing I've seen a few times, so that's why originality is four stars.
the background, mainly the sky, looks so awesome with all the colors you used, and I love how you drew the clouds.
in a nutshell, this picture is beautiful and adorable. I love your drawing style, it's so cute. great job~! (hopefully this critique was good :T)