Admittedly I'm biased because sylph of rage is my classpect even if I didn't suggest it, but i don't think sylph of rage is necessarily negative. Leaving aside that anger is not necessarily unneeded or unproductive, things including the Extended Zodiac and (probably) Yiffy's narration associate it with painful truths and the destruction of comforting illusions. A sylph of rage could just as easily be someone who breaks down toxic positivity and a refusal to confront actual problems, or who makes people apply their anger constructively