Al Capone may have been the single most notorious gangster in American history, commanding respect and inspiring fear throughout Chicago and beyond, but the real life "Scarface" went out with a whimper, not a bang.
Though he never commented on it, Capone was believed to have exhibited symptoms of Syphilis from his early teen years. Though the sexually transmitted disease was treatable, Capone feared needles and was embarrassed by his symptoms. Since they consistently retreated, he reasoned he wasn't truly sick.
After making his name in the violent Chicago Beer Wars, Capone was convicted of tax evasion in 1931. As he set off on an 11-year sentence, he was officially diagnosed with Neurosyphilis, along with gonorrhea.
Over five years at Alcatraz, the erstwhile mafioso's mental state declined steadily as the disease attacked his brain. Eventually, he regressed to such an extent that he was no longer a threat to anyone, and he was paroled in 1939. He lived out his days in a childlike state, looking at butterflies and hallucinating conversations with old friends from his outlaw days.