I don't think Peeta gets scared or intimidated very easily. He has a quiet confidence. I don't see him being afraid of Katniss's anger. He would probably just respond to it very patiently and honestly. In fact, I see her being more afraid of him, because she has a tendency to deny reality.

If she was mad he would probably be there just listening to her yell the whole day until she's calm down again! I don't see how he could be afraid of Katniss, even after everything, in the end he's still seeing the good on her!

Afraid??? lol

I don't think he'd be afraid of her. He trusts her enough to know she wouldn't vent her anger on him. Maybe he'd be afraid for her in the sense of what she might do with her anger and the consequences.