Came into my mind after my Necrowarrior got her necro-ass kicked several times.
So yeah, my Necrowarrior is very powerfull, no doubt. It's not just her frost magic. Which is quite weak, actually. Mainly usefull to put an end to weak groups and looking cool. (Pun intended.) What makes her especially powerfull is her skill in the blade and her ability to raise powerfull undead.
Her weak spot however? Surprisingly enough, it's probably lightning. Fire she can handle most times, and frost is often like the bite of a flee. But a strong lightning spell from a strong mage can be fatal if she isn't wary. Especially chain lightning is dangerous, for it could damage her when one of her undead gets hit with it.
To keep it short.
People who come close to her are doomed. People with lightning who stay at a distance will kick her back into her grave. She isn't actually undead but whatever.