Jamieson, Fausset and Brown on 2 Corinthians 11:21

21. as concerning reproach--rather, "by way of dishonor (that is, self-disparagement) I say it."

as though we ... weak--in not similarly (2Co 11:20) showing our power over you. "An ironical reminiscence of his own abstinence when among them from all these acts of self-exaltation at their expense" (as if such abstinence was weakness) [Alford]. The "we" is emphatically contrasted with the false teachers who so oppressively displayed their power. I speak so as though WE had been weak when with you, because we did not show our power this way. Howbeit (we are not really weak; for), whereinsoever any is bold ... I am bold also.