Dean held Cas' gaze for a long, tense moment. He could either turn away and let the moment fade (and the tension build) or he could satisfy his need to hit something repeatedly. It was dangerous territory, but this would hardly be the first time he'd pummeled Cas, and likely not the last.
Cas understood Dean in a way no one else could. He'd been there, he'd been the one to pick up the pieces after...Dean shut his eyes. He raised his hand to press his fingers to his temples, trying to push back those thoughts of Sam, of what Sam did, what he became.
His eyes opened and his hand didn't so much drop as it shot out to again connect with Cas' face, countered by an assault from the other side. "Hit me back, you son of a bitch. Hit me," Dean growled.