Intensifiers can slightly increase the effectiveness of your message, but understatement, for example using litotes, can make your ideas more memorable and boost the overall effectiveness of your point. Ancient and modern orators used understatement to show modesty and so to make their audience better disposed. But understatement can also intensify your point.
Litotes is one of the most popular figures of speech used for understatement. With litotes you deny the opposite of what you want to say. For example, you want to say that oil spills are very bad for environmental conservation. So you take the opposite of ‘bad’ – “good” – and deny it: “oil spills are not very good for environmental conservation.”
Here are a few superior examples:
“In his youth, however, though too imbecile for study or for business, he was not incapable of being amused.”
(Thomas B. Macaulay, The History of England from the Accession of James II).
“It was not without satisfaction that I recognised my own handiwork in a great cut under his right eye, and a considerable discolouration round the socket.”
(Robert Louis Stevenson, New Arabian Nights, 1882)