In the center of the lowest level of Dantes Inferno, Satan,
lies with half his body trapped in ice. He has three faces,
six wings, and fur (all features of various dragons). This
image shows an engraving by Gustave Dore.
It's interesting, but not surprising, that Dante Alighieri's description, and Gustave Doré's depiction of Satan in Dantes Inferno are distinctly dragon-like. In fact, Western dragons are typically evil and often represent the devil. In A Study of Dragons East and West, Qiguang Zhao writes "The Western idea of the dragon as a symbol of the satanic in nature is very very old" (Peter Lang, 1992).
The only thing that seems out of place here (with both Western depictions of dragons, and classic descriptions of Hell) is that the fire is missing. Even the word inferno conjures up a blast furnace, but in Dante's center of Hell, it's all ice.
Fire and ice aside, are dragons traitors? They can be cunning and deceptive, and in that sense they can be described as treacherous, but one might argue it's a human's mistake to trust them in the first place.
The typical evil dragon is solitary, selfish, and without remorse. It has no loyalty or solidarity with anyone, and no one expects it to be merciful. It is amoral. These dragons are deadly but they can't be treacherous for they have no one to betray.
In contrast, lots of dragon stories, old and new, depict dragons who have relationships with humans, from the Colchian dragon who guarded the golden fleece for Aeëtes, King of Colchis, to the dragon steeds of Anne McCaffrey's Pern novels. Some are basically evil; some are not, but typically these dragons don't willfully betray their human counterparts.
Clearly, dragons aren't necessarily traitors, so they don't live up to the Western idea that they represent the devil (or at least Dante's devil). Perhaps the entity in the center of the inferno is the ultimate sinner, the ultimate traitor, and the ultimate (evil) dragon, but like the entities in the nine levels of Dante's Inferno and in the world above, there are many degrees and variations of each.