First of all: This is amazing. And I'll explain what I find amazing about it right after this;
Pokemon fusions are bit weird, and it isn't because that they are bad. I think a lot of artists get away with using Pokefusions as an inspiration, and create something that loses both essences but looks nice on its own. It is why realistic pokemon renders look a bit weird, as many artists just make things up and forget about the actual pokemon. It is possible to make realistic pokemon renders, as long as they use the essence of the pokemons. Now, my opinion aside, although I absolutely love your final product as a concept--I do kind of miss the very essences of both pokemon in your pokefusion. If you weren't going for a proper pokefusion, but rather just took the idea and went with it, then this would be amazing. But, I'll assume this is a pokefusion.
At first glance, you should be able to tell what you are looking at. Unless this is conceptual art (within modern art), or contemporary art, or any type of art that requires thinking and considering, then it needs to be very clear from first glance. Mostly because, most people don't stare at a picture for more than a few seconds, and by then, you might have lost them.
Now, do I see what is going on in the first picture? Yes. But not because of your creation, more because of the team rocket person standing off to the right. And this is a really good trick, her hair being green contrasts well with the overwhelming red in the background, dragging our eyes to her and forcing us to recognize what is going on. This is where the problem begins, however. "Oh, team rocket. Are they using monsters now?"
In essence, pokemons are monsters. The very name of the brand, used to be Pocket Monsters. Looking at the concept, it is more realistic than regular pokemon. So, not only do we have texture, lighting, ANATOMY (your creature inhabits more anatomical details than regular pokemon), but we have a very different creation.
Taking away the team rocket person, and the weezing icon, this would've been a very interesting standalone concept. You have a disgusting, creepy looking chimera that wields fire and gas, which is ground for only devastation. A being that uses explosions at will, and that inhabits the power of flight, and the savageness of a raptor. There are plenty of good things going on here, you have a complex and almost contradictory concept (gas and flames) that sparks both interest and that have a real function in real life (explosions), and you have a giant being that wields this, with two furiously sharp raptor like heads, that even has wings. It is really interesting, and it is really good looking.
Now, if this wasn't a pokefusion, I would go over to background, colors and other things. But, I'll go over what you could do, to capture their essence into this thing.
First of all--I would add more colors. Specifically, I want Weezing's icon to stand out and show others that it isn't just a patch of skin on his torso. As it stands, it is a nice color. The problem is, the entire dragon is red, and this blends right in. You can make this far more interesting by adding a secondary color to the design, and playing off the two by altering saturation. Orange, red and pink is too red, especially when this is supposed to be two pokemon.
This one might be tricky, but you might have to do something with the proportions. Proportions on its own is very important, as it often is the difference between a human, and an alien (heads being wrong). Your creature has completely different proportions, making it new and unique. Your proportions are so vastly different, that the being is standing on two front arms, which is also completely new, as Weezing has none, and charizard has two arms and wings. Now, again, I've explained how much I adore this design. But making so many new things, only alienates us from what it is supposed to be. I've mentioned how the anatomy was more realistic, and this is just an extension of that (that and his chicken feet 
). There are other points that are very realistic as well, such as his heads and long tail. The tail needs to be large, for a being this size, and his heads resemble more of a raptor than a Charizard. And a final point; the black skin texture that covers his back and front wings look awesome, but are completely new as well.
Now, lets go over background. There isn't much going on and I think it sort of speaks for it self, my main issue with it is the quite desaturated line that is right behind Charizard. It is a problem, because it almost looks like the horizontal line, throwing off the viewers. Now, even though it ISN'T that, another general art rule is to always avoid things that seem like a mistake. Such as in composition, two lines meeting each other even though there is nothing there. Not only does this line make the creature seem weird, but it also further breaks whatever kept the creature grounded. His shadow is very slim and does not interact with the floor whatsoever. Besides the blur that is the background, the ground is kind of messy as well. And that is fine, but the main issue is the edge down to the left. It gives away the perspective, making us view from above. And we can see the top of the small head, which is great! We also see the top of this team rocket character, enforcing that. And there is nothing really wrong, besides that it is a weird place to place the viewer. The perspective seems a bit off as well.
Hopefully this was of some help!
