I think as a doctor, the most daring and difficult thing to say to a patient is certainly informing them about a life-threatening disease living inside of them. Most of the time, the patients expect the earth-shaking news to be backed up by a piece of good news such as, 'but this treatment will work', 'I assure you, you're going to be okay'. 

However, this one time I had to break dreading news like that to my patient, and no matter how much I insisted that she was going to be okay, she refused to believe me. So, I had to put on my brave face and help her walk to the possibility of fatality and how it wouldn't be bad either. That's easily one of the most daring things I've said to a patient