Dead End allows Knock Out to do what he wants, quietly commenting on how it would figure that he's probably broken beyond repair. Wouldn't surprise him, and considering everything he's been through in his life up to this point, it's amazing it hadn't happened sooner.

He's not doubting the medic's skills, he's just doubting life.

Nothing new there.

"I shouldn't have done it to begin with. And he wasn't."

Sure he didn't ask or even think about that, but it seemed pretty clear that Rung wasn't into the idea.