「全く」(まったく) functions as an adverb meaning "completely" or "entirely." When used with a negative verb, it translates to "not at all" or "not in the least," indicating absolute negation. When used with a positive statement, it means "completely" or "really." Example: 彼の話は全く理解できませんでした。 (I couldn't understand his story at all.)

完全に、少しも〜ない（否定文）。