I'm not quite sure what's the rule for using 全くand 決して in negative sentences. I always have like a feeling which one to use in quizzes, but I'm not sure what the rule behind it is...
全く is more like "doesn't X at all" and 決して is more like "absolutely won't X". 全く has more to do with what's actually not being done and 決して about the intention not to do it.
It might help to think of them in terms of what their kanji mean; 全 is "all" (or "not at all" since it's negative), 決 is "decision" (or "decidedly" avoiding doing something).
全く is more like "doesn't X at all" and 決して is more like "absolutely won't X". 全く has more to do with what's actually not being done and 決して about the intention not to do it.
It might help to think of them in terms of what their kanji mean; 全 is "all" (or "not at all" since it's negative), 決 is "decision" (or "decidedly" avoiding doing something).
