An adverb that negates a statement is called an adverb of negation.
- She is not at all happy with the outcome
- No, I have not won the lottery.
- By no means will he do so.
- I am certainly not crazy to risk my life in such an adventure.
The highlighted words not at all, no, by no means and certainly not negate their respective statements. Therefore, they are adverbs of negation.