Cerberus, the Incompetent Watchdog of Hades
From fifty-headed primordial monstrous canine to three-headed pet of Hades, Cerberus is renowned for being the vicious guard dog of the Greek and Roman underworld, tasked with keeping the dead in and the living out. But his reputation seems largely unearned, given the rather large number of live humans who managed to infiltrate Hades.