The blue haired demon didn't have to be able to hear to know he was being mocked. It was clear from the expression on Hamel's face. Well, that was it. No more messing around.

Laharl's face stoned serious as he watched Hamel's mouth open and close as he continued to heckle the Overlord. Glaring coldly at Hamel, he started to release his power, it flaring around him dramatically before he gathered it to his hand. "Shut up, you bastard," he hissed, forming an orb of energy that he promptly released towards Hamel, where upon whatever it hit first, would explode.

Either he'd hit the bastard and wipe that grin off his face, or blow an impressive hole out the back of the theatre. Either way, it would hopefully deliver a message that Laharl was a very serious threat here.