Druddigon: The Cave Pokemon.
Flavor text: It warms its body by absorbing sunlight with its wings. When its body temperature falls, it can no longer move. It races through narrow caves, using its sharp claws to catch prey. The skin on its face is harder than a rock.
First problem with Druddigon: its skin pigmentation. If it really is a Pokemon that lives primarily in caves, and races around underground, the fact of the matter is that it evolving such colors as bright blue and red and yellow and, in rare cases, green are illogical. Most cave-dwelling, underground creatures develop little color because there’s no need for it underground in a near-lightless environment.
Second problem: while the flavor text says that Druddigon “races through caves”, Druddigon’s base speed makes him amongst the slowest of all the Pokemon of 5th gen. Along with his remarkably low Special Attack, its Attack is really the best stat it can use to attack prey, and even if it chased down another cave-dwelling Pokemon, Ferrothorn, it’s unlikely it could do much damage to one without breeding giving it the superior edge. Druddigon is almost more suited for prey than it is for predator.
Third problem: Druddigon is dependant on sunlight and warmth to keep itself mobile, mainly by absorbing sunlight and heat through its wings in order to keep its body warm. Druddigon lives in caves. How on earth does it expect to get sunlight in a mostly lightless environment? Unless it surfaces to bask in the sun for several hours outside its natural habitat just to run around caves at night catching its food, it seems highly illogical for a cave-dweller to need sunlight in order to function, lest it become unable to move and perhaps even die.
All in all, especially with the lack of attacks that are truly affected by one of its abilities, Sheer Force, Druddigon in the wild is theoretically an evolutionary failure, and, invasive foreign species excluded, has the very real possibility that it could be outperformed by many other of Unova’s species (oh, wait, nevermind).