Rhetorical device works by attempting to make someone or something less significant important?

The rhetorical device that works by attempting to make someone or something less significant is called "Litotes". Litotes is a figure of speech that expresses a positive by negating its opposite. Instead of saying "She was very intelligent", one might say "She was not unintelligent". This form of understatement can be used to emphasize a point, to create a sense of irony, or to convey a sense of modesty.