Well, he supposedly took about 200 gold signet rings off the bodies of dead upper-class Roman citizens after Cannae and sent them back to Carthage to be dumped in front of the Carthaginian senate to convince them he had Rome on the ropes. Most of our sources on Hannibal were written by his Roman enemies and so are not entirely reliable when judging the man. He is generally portrayed in those sources as quite savage and bloodthirsty. Roman writers of later generations had good reason to cast Hannibal as a monster -- it made the Roman victory over him seem even more impressive and noble.