Not long ago, Thomas DiFiore cut an intimidating figure. For a time, he was the highest-ranking member of the Bonanno organized crime family not behind bars, despite a long record of arrests on charges of kidnapping, assault, promoting gambling and extortion. Even at 70, Mr. DiFiore did not seem to falter when challenging another aging Bonanno leader in 2013 for more than his share of a loan payment, according to prosecutors’ account of a government wiretap.

“ ‘Without me,’ ” the other leader, Vincent Asaro, recalled Mr. DiFiore telling him, “ ‘you wouldn’t a got nothing.’ ” Mr. Asaro, whose words were being recorded by the Federal Bureau of Investigation, said Mr. DiFiore made a former Bonanno boss “look like St. Anthony.”

Yet now, as he faces sentencing for federal unlawful debt-collection conspiracy, Mr. DiFiore’s swagger has given way to a shuffle, and he is talking about insulin and statins rather than payback.

He is one of the “oldfellas,” Mafiosi whose lives of crime seem to have succumbed as much to the ravages of age as to the relentlessness of federal prosecutors. In courtrooms, they can be found displaying catheter bags or discussing the state of their kidneys in hopes that a judge will agree to a short sentence.