Not too surprising to me, actually! I totally expected the brutality. Lelouch, after all, represents everything that Suzaku wanted to rid himself of. He's just shifted from kicking himself to taking it out on Lelouch first—and considering how little allowance Suzaku shows for himself in the past (see: the final picture drama), it's not surprising that he'd be so violent on this real life equivalent to what he feels are sins.