Just a quick list of Claire's MAJOR weaknesses.

Dark Magic- Since shi's a Light Dragon, Dark anything hurts hir immensely. Even the weakest of Dark stuff can cause hir major pain. Dark Magic is also poisonous to hir.
Corruption- Makes hir mind and intellegence take a major nosedive. But, thankfully, shi can speak one language completely. Even if it's a little delayed sometimes. Hir natural language is the Dragon Language from Skyrim.
Radiation- Do I need to offer explanation? It's too Rad.



BTW, characters like Cynder, Spyro, etc. are all considered Ancestors to Claire.