Well, maybe Edward of Lancaster as well.
Both Joffrey and Edward had sadistic tendencies, with the latter (and, to be fair, the former) taking particular pleasure in torturing and then executing his enemies. Both shared a questionable legitimacy, although Edward never tasted real power as he was killed during the Battle of Tewkesbury, one of the decisive battles of the War of the Roses.
Caligula, however, did reach power and was just as cruelly insane as Joffrey. He murdered many of his relatives, confiscated large swathes of peoples property, and famously made his horse a senator. He also died young, although he was stabbed to death as opposed to the more theatrical poisoning Joffrey received.