I don't know what to tell you
A rude way of saying you're giving up on someone and you're not going to bother trying to fix their mess.
My dad said, "I don't know what to tell you" after I spilled my cereal all over the floor.
My brother said, "I don't know what to tell you" when I told him I lost my phone.
My friend said, "I don't know what to tell you" after I failed my science project for the third time.