I know the story of an older woman who was a witch and, for example, could identify the source of malicious magic using candles. Once, she performed a harmful spell to kill a man who had abused a child. The man’s wealthy family hired a magician, and the woman woke up feeling as if her entire body was burning. She suffered a barely visible aneurysm and died a few days later.
The invisibility ability mentioned in some grimoires could be a way to avoid detection—beyond the metaphor of the ‘gray man’ (entering a place you not must enter, but doing so with such calm and confidence that no one suspects you). Or perhaps one could work with Azazel and use another enemy as a scapegoat, killing two birds with one stone.