What song lyrics have understatement (litotes)?
"Is it still over?" by Randy Travis.
A figure of speech consisting of an understatement in which an affirmative is expressed by negating its opposite, as in This is no small problem, or "He's not bad looking".
One of my favorite lines:
"Since my phone still ain't ringing, I assume it still ain't you."
I'm sure you can think of others, now that you know what to look for.